Author Archives: raulg

Creating a callable Toast component in Svelte using bind:this (DaisyUI optional)

I’m using Svelte+Kit for new development, and also starting to use DaisyUI, i found a need to use the Toast component to show a message which appears for a while, then disappears, such as an error message on a form submit, or a success message.

Creating a Svelte component called Toast.svelte would be easy. The challenge is to wrap a callable function to invoke the functionality which would:

  • make the Toast visible
  • set the message, and the alert style (success, error, etc)
  • allow it to disappear after X seconds automatically

To start, i made the simple component, which would have an exported message and alerttype props.

<script lang="ts">
export let message = '';
export let alerttype = 'alert-error';
</script>

<div class="toast toast-top toast-start z-40">
    {#if message}
    <div class="alert {alerttype}">
        <div>
            <span>{message}</span>
        </div>
    </div>
    {/if}
</div>

That allowed me to invoke the Toast from the parent +page.svelte like so:

<script lang="ts">
export let toastMessage = 'some error message';
export let toastAlertType = 'alert-error';
</script>

<Toast message={toastMessage} alerttype={toastAlertType} />

Then i could write a page-level function callToast(), or even a *.ts library, but that was too messy. I want the callable function withing the same Toast.svelte component file.

I did it using the Svelte bind:this element directive.

./components/Toast.svelte

<script lang="ts">
let message = '';
let alerttype = 'alert-error';

// https://akashmittal.com/svelte-calling-function-child-parent/
// call from parent as: 
// let toast: Toast;
// toast.callToast(message, alerttype);
// <Toast bind:this={toast} />

export function callToast(msg: string, type?: string|undefined, ms?: number|undefined) {
    console.log('callToast()');
    let milliseconds: number = 8000;
    if(ms) { milliseconds = ms; }
    if(type) { alerttype = `alert-${type}`; }
    message = msg;

    setTimeout(() => {
        message = '';
    }, milliseconds);
}

</script>

<div class="toast toast-top toast-start z-40">
    {#if message}
    <div class="alert {alerttype}">
        <div>
            <span>{message}</span>
        </div>
    </div>
    {/if}
</div>

+page.svelte:

<script lang="ts">
    import Toast from "$components/Toast.svelte";
    let toast: Toast;
</script>

<Toast bind:this={toast} />

<button on:click={() => toast.callToast('testing this toast notification...', 'error')} class="btn">toast test</button>

Depending on your coding style, this may be easier than using a third-party library.

References:

https://akashmittal.com/svelte-calling-function-child-parent/

Tan Li Hau – Svelte Tutorial for Beginners – bind:this

QRcode component in Svelte, featuring bind:this

I was just porting a hybrid mobile web app from Ionic+Angular to SvelteKit+Capacitor, and there was a qrcode generator page, where a number of qrcodes get generated in a sequence.

I wasn’t happy with the custom libraries so i opted to use the generate node-qrcode package, which supports the ESM import syntax. Some other libs expect you to import a script over the web, but i need something that will package up (Vite+capacitor).

The problem i had is that the example code uses a <canvas> element, which gets populated via DOM manipulation:

<!-- index.html -->
<html>
  <body>
    <canvas id="canvas"></canvas>
    <script src="bundle.js"></script>
  </body>
</html>
// index.js -> bundle.js
var QRCode = require('qrcode')
var canvas = document.getElementById('canvas')

QRCode.toCanvas(canvas, 'sample text', function (error) {
  if (error) console.error(error)
  console.log('success!');
})

My approach was to put the above code in a svelte component (Qrcode.svelte) which would do the work. Then its is called like so:

<!-- +page.svelte -->
<script lang="ts">
import Qrcode from '$components/Qrcode.svelte';
import { writable, type Writable } from 'svelte/store';

let tagIds: Writable<Array<string>> = writable(['101', '102', '103', '104']);
let qrcodeWidth = '160';
</script>

<div>
  <div>
    {#each $tagIds as tagId}
      <Qrcode value={tagId} width={qrcodeWidth} errorCorrection="M" />
      <div class="tagid-caption">{tagId}</div>
    {/each}
  </div>
</div>

Now the problem is that only one qrcode gets written:

The reason is that when svelte creates each component in the DOM, they will all have the same ID, which we definitely don’t want – each ID and code must be unique.

It turns out the “right way” to address a DOM element in a Svelte component is to use the bind:this syntax.

We create a variable for the canvas element, use bind:this={canvas} in the <canvas> html tag, and in onMount(), QRCode.toCanvas(canvas).

<!-- Qrcode.svelte -->
<script>
import QRCode from 'qrcode';
import { onMount } from 'svelte';

// https://stackoverflow.com/a/58015980/408747
// we use bind:this so this component can bind qrcode to the particular canvas in the DOM
// svelte will create unique DOM ids for each component
let canvas;

export let value = '';
export let width = '200';
export let errorCorrectionLevel = 'M';

const options = {
    errorCorrectionLevel,
    width,
};

onMount(() => {
    QRCode.toCanvas(canvas, value, options, function (error) {
        if (error) console.error(error);
    })
});

</script>

<canvas bind:this={canvas}></canvas>

Now we have canvas elements w/unique qrcodes, using a normal Svelte component and a vanilla ESM JavaScript QRcode library. 😊

Update: after posting, i just was made aware of a new svelte qrcode generator package – phippsytech/svelte-qrious. It uses the bind:this in the component definition, like i explained. But it’s an installable npm package, with a REPL.

Nhost Hasura Auth + SvelteKit implemented simply

This is a short and sweet example of using a SvelteKit frontend project with Nhost authentication.

Overview

Nhost is the serverless backend built on Hasura (graphql server backend). NHost is built on it’s open source Hasura Auth library (using JWTs). They are nearing v2 official release and have sample templates for React and Next.js, but not Svelte yet, so i thought i’d show a simple implementation.

I went through the rationale for using Svelte and Hasura in a prior post. As for why to use Nhost, i see some big pluses:

  • Open Source 100%: it is possible to self-host the entire system if you want to leave the provider for any reason. This is big for me.
  • Integrated with and built on Hasura: I already decided on using Hasura for it’s role-based authorization, low-code model on top of real relational dbs like PostgreSQL.
  • Fills needed gaps in Hasura: authentication and storage.

To demonstrate, i’m going to rely on a few things in Svelte and Nhost, which can hook up nicely:

  • Svelte writable() store to observe changes in the authentication status and logged in user, and re-render UX component changes in real-time.
  • Nhost auth’s onAuthStateChanged() event handler, which will update the writable() stores whenever a user is logged in or out, or their token expires.

Combining an auth state change handler with an Observable Svelte store linked to a UI component – will ensure authentication always is in sync with the user interface, using the least friction in the code. Less bloat == less bugs.

Those are the main things. I’ll also implement a SvelteKit layout, couple pages to route, a login form / logout button, and “login status box” component which can be included in various places on the app. Plus a Vite .env file, just because its the SvelteKit way and Vite rocks super fast (transpilers to ES5 need to die). I may use TypeScript, but Javascript works just as well (except for the bug in my event handler which i didn’t find until using TS 😡).

Create Nhost Project

Nhost.io is a backend as a service provider, built using Hasura plus Nhost’s own open source Hasura Auth and storage (AWS style). They have a CLI for running locally on your dev machine in a container, but for this demonstration, i will just create a new free service.

Once you have a login registered (Github login supported),

  • create or select a workspace
  • create a new App (select region, and free plan)

Once the app is deployed, you can copy the Nhost backend url ( https://{long-identifier}.nhost.run ), which you will need to access in your project’s .env file. Also available are tabs for:

  • Hasura Console (w/admin secret)
  • User Management (a simply UI for managing user records, which your app will use)
  • Storage (for any future file storage your app uses)

Typically, your application will access resources with these users. When you design your app, you will configure roles for authorization to your Hasura resources, and the Nhost user roles will also map to the same roles.

Typically, the anonymous role is “anonymous” or “public”. It’s configurable.

In my opinion, the role authorization system is a major plus of this backend stack. Since they use JWTs, it can scale out to multiple Hasura instances and even other backends, as long as they support JSON Web Tokens and are configured with a shared secret. And Hasura’s row-level authorization has the potential to cut out tons of boilerplate code for authorization.

Create SvelteKit Project

Next, let’s create a SvelteKit project with __layout.svelte and a couple pages.

npm init svelte nhost-sveltekit-auth-test
cd nhost-sveltekit-auth-test
code .

We’re going to have an index page, login page (which will later switch between a login form and a logout function, depending on status), and the layout page will contain a simple navigation, as well as a little component.

Plus a dotenv file, Vite-style.

# .env
VITE_NHOST_BACKEND_URL=https://{long-identifier}.nhost.run
<!-- src/routes/index.svelte -->
<h1>Nhost on SvelteKit</h1>

<p>
    Testing Nhost hasura-auth, onAuthStateChanged event with svelte store. 
</p>
<p>
    Go to <a href="/login">Login Page</a>
</p>
<!-- src/routes/__layout.svelte -->
<script>
	import LoginStatusBox from '$lib/components/LoginStatusBox.svelte';
</script>

<LoginStatusBox />

<div>
	<h1>Nhost Hasura Auth + SvelteKit</h1>
	<main>
		<slot />
	</main>
</div>
<div>
	<section class="nav">
		<ul>
			<li><a href="/">Home</a></li>
			<li><a href="/login">Login</a></li>
		</ul>
	</section>
</div>

npm install nhost

npm install @nhost/nhost-js

Create $lib/nhost.ts|.js

// nhost client

import { NhostClient, type NhostClientConstructorParams } from "@nhost/nhost-js";
import { writable } from "svelte/store";

export const VITE_NHOST_BACKEND_URL = import.meta.env.VITE_NHOST_BACKEND_URL as string;

export const config: NhostClientConstructorParams = {
    backendUrl: VITE_NHOST_BACKEND_URL,
};

export const nhost = new NhostClient(config);

// store
export const isSignedIn = writable(null);
export const user = writable(null);

nhost.auth.onAuthStateChanged(
    (event, session) => {
        console.log(`auth state changed. State is now ${event} with session: `, session);
        if (event === 'SIGNED_IN') {
            isSignedIn.set(true);
            user.set(session?.user);
        }
        else {
            isSignedIn.set(false);
            user.set(null);
        }
    }
);

export async function signIn(parameters) {
    // console.log("signIn(parameters): ", parameters);

    let params = {
        email: parameters.email,
        password: parameters.password,
    };

    if (parameters.email) {
        params.email = parameters.email;
    }
    if (parameters.password) {
        params.password = parameters.password;
    }

    // TODO: sanitize inputs

    const data = await nhost.auth.signIn(params);

    return {
        ...data,
    };
}

nhost.auth.onAuthStateChanged() handler

By leveraging Nhost’s onAuthStateChanged() event handler, every time there is an authentication change (signin, signout, for any reason like user-initiated or token expriation), we update the svelte stores/observables with the updated values. In turn, all the components can immediately re-render to update based on the new state. That includes both the login form, as well as the status box component, appearing all over the application. With very little code involved.

Create a login.svelte page and wire it up

<!-- src/routes/login.svelte -->
<script>
    import { isSignedIn, nhost, signIn, user } from '$lib/nhost';

    let loginMessage = '';

    async function loginFormSubmit(e) {
		console.log('loginFormSubmit()');
		const formData = new FormData(e.target);
		const submitData = {};
		for (let field of formData) {
			const [key, value] = field;
			submitData[key] = value;
		}
		console.log("submitData: ", submitData);
		const data = await signIn(submitData);
		console.log(data);
        if(data.error) {
            loginMessage = data.error.message;
        }
        else {
            loginMessage = "login success";
        }
	}

</script>

login

<div style="color:red">
    {loginMessage}
</div>

{#if $isSignedIn && $user}
    <div>you are signed in, {$user.displayName}</div>
    <div><a href="#signout" on:click={()=> nhost.auth.signOut()}>sign out</a></div>
{:else if $isSignedIn === false}
    <div>please log in</div>

    <form on:submit|preventDefault={loginFormSubmit}>
        <div class="form-item-wrapper">
			<label for="email" class="form-label">Email</label>
			<input name="email" type="text" placeholder="Email" class="form-field" />
		</div>
		<div class="form-item-wrapper">
			<label for="password" class="form-label">Password</label>
			<input name="password" type="password" placeholder="Password" class="form-field" />
		</div>

		<input type="submit" value="Log In" />
    </form>

{:else}
    <div>Page loading...</div>
{/if}

Create a “login status box” for display on navigation or other places all around the site/app

<!-- src/lib/components/LoginStatusBox.svelte -->
<script>
import { isSignedIn, user } from "$lib/nhost";
</script>

<div class="loginstatus">

{#if $isSignedIn && $user}
<div>Aloha {$user.displayName}</div>
{:else}
<a href="/login">Login</a>
{/if}

</div>

<style>
    .loginstatus {
        border-style: dotted;
        border-color: gray;
        display: flex;
        width: fit-content;
    }
</style>

Conclusions

What i found:

  • Implementing Nhost’s Hasura Auth is relatively simple
  • Its onAuthStateChanged() handler can map easily to a Svelte store for reactive UX.

Source code on github: https://github.com/nohea/enehana-nhost-sveltekit-auth

This coding video is on YouTube:

References

Extra Credit

I found there is a token change event handler onTokenChanged() , which can be used to update any JWT store observable you may use.

Svelte Complex Forms, part 3 – components using get/setContext() for less passing props

In my prior two posts, i created a more complex dynamic and hierarchical form, including radio buttons, and extracted the “sveltey” html into a couple components.

In this post, i’m refining my components a bit, to reduce the boilerplate attributes needed for each instance. Currently, they look like this:

<ZInput
	nameAttr="fullname"
	nameLabel="Full Name"
	bindValue={$form.fullname}
	errorText={$errors?.fullname}
	{handleChange}
/>

<ZRadio
	nameAttr="prefix"
	nameLabel="Prefix"
	itemList={prefixOptions}
	itemValueChecked="n/a"
	errorText={$errors?.prefix}
	{handleChange}></ZRadio>

I would like to remove the errorText and handleChange props, even the bindValue if possible.

To bypass explicit props just to reference the $errors object and the handleChange functions, i’ll use Svelte’s getContext() and setContext(). I borrowed it from the svelte-forms-lib optional components, but mine are different in that they also include a <label> and $errors indicator. For a great explanation of Svelte Context, see Tan Li Hau’s Store vs Context tweet/video.

In the form.svelte page, it contains the bare <form> element, and the createForm() call which returns $form, $errors, and the handle* functions. We add new setContext() call, setting those objects. This will allow child components to getContext() and access the same objects, without requiring them to be passed in via props.

const { form, errors, state, handleChange, handleSubmit, handleReset } 
  = createForm(formProps);

// allows for referencing the internal $form and $errors from this page, 
// so we can add the array handlers
setContext(key, {
	form,
	errors,
	handleChange,
	handleSubmit,
});

Now in the child components, add getContext() and modify the use.

ZInput <script> section:

// allows the Form* components to share state with the parent form
const { form, errors, handleChange } = getContext(key);

Then we won’t have to pass in those objects via prop. However, we still have a problem…

Impedance-mismatch: flat $errors keys vs. hierarchical $forms object

As discussed in my prior post, the underlying $form store is “flat”, but the underlying svelte store is hierarchical, meaning we have to refer to $form by that flat key. For example:

$form$errors
$form[‘fullname’]$errors.fullname
$form[‘profile.address’]$errors.profile.address

$form[‘contacts[0].name’]

$errors.contacts[0].name
$form[‘contacts[2].name’]$errors.contacts[2].name

I think this is the inevitable mismatch where the html form has a list of flat “name”s in a traditional POST, but the data it is handling is hierarchical.

If we try to use the key passed in for “name”, it won’t work to find the matching error message. So we have to convert the string key “contacts[2].name” to the equivalent object reference $errors.contacts[2].name in order to display the linked error message (if any).

I ended up using a function from stack overflow, which allows me to pass in an object, and a string key, which returns the value from the object the string key would point to:

// window.a = {b: {c: {d: {etc: 'success'}}}}
// getScopedObj(window, `a.b.c.d.etc`)             // success
// getScopedObj(window, `a['b']["c"].d.etc`)       // success
// getScopedObj(window, `a['INVALID']["c"].d.etc`) // undefined
export function getScopedObj(scope, str) {
    // console.log(`getScopedObj(scope, ${str})`);
    let obj = scope, arr;

    try {
        arr = str.split(/[\[\]\.]/) // split by [,],.
            .filter(el => el)             // filter out empty one
            .map(el => el.replace(/^['"]+|['"]+$/g, '')); // remove string quotation
        arr.forEach(el => obj = obj[el])
    } catch (e) {
        obj = undefined;
    }

    return obj;
}

Then my final component looks like this:

<script>
    import { getScopedObj } from "$lib/util";
    import { getContext } from "svelte";
    import { key } from "svelte-forms-lib";
    export let nameAttr;
    export let nameLabel;
    export let bindValue;
    // allows the Form* components to share state with the parent form
    const { form, errors, handleChange } = getContext(key);
</script>
<div>
    <label for={nameAttr}>{nameLabel}</label>
    <input
        placeholder={nameLabel}
        name={nameAttr}
        on:change={handleChange}
        on:blur={handleChange}
        bind:value={bindValue}
    />
    {#if getScopedObj($errors, nameAttr)}
        <div class="form-error">{getScopedObj($errors, nameAttr)}</div>
    {/if}
</div>

<ZRadio> can be modified in a similar way. Now the component tags are more concise:

<ZInput
	nameAttr={`contacts[${j}].email`}
	nameLabel="Email"
	bindValue={$form.contacts[j].email}
	/>

<ZRadio
	nameAttr={`contacts[${j}].contacttype`}
	nameLabel="Contact Type"
	itemList={contactTypes}
	itemValueChecked="n/a"
	/>

… and the user behavior is the same.

code for part 3 is at:

https://github.com/nohea/enehana-complex-svelte-form/tree/part3

Svelte Complex Forms, part 2 – refactoring into custom components

As a followup to my last post Svelte Complex Forms with radio buttons, dynamic arrays, and Validation (svelte-forms-lib and yup), i created a more complex dynamic and hierarchical form, including radio buttons. I was glad it worked, but not happy about the more complex array prefixing.

In this post, i will attempt to extract the “sveltey” html into a couple components. I’ll just name them with a Z-prefix for kicks.

  • a component with the label + input type=text + error (ZInput)
  • a component with the label + input type=radio + error (ZRadio)

Creating them under src/lib/c/*.svelte

The idea here is to supply all the variables in the component as props (a la Component
Format
), so the components are relatively generalized in the app, and we can set them in our existing each loops for the form.

ZInput : input type=text

Let’s start simple – the text input. Our first example looks like this:

<div>
	<label for="fullname"> Full Name </label>
	<input
		type="text"
		name="fullname"
		bind:value={$form.fullname}
		class=""
		placeholder="Full Name"
		on:change={handleChange}
		on:blur={handleChange}
	/>
	{#if $errors.fullname}
		<div class="error-text">{$errors.fullname}</div>
	{/if}
</div>

The props to extract could look to be:

  • nameAttr (fullname)
  • nameLabel (Full Name)
  • bindValue ($form.fullname)
  • errorText ($errors.fullname)
  • handleChange (needs to be referenced to the parent page/component)

Looking at the more nested example, the same props apply:

<div>
	<label for={`contacts[${j}].email`}>Email</label>
	<input
		placeholder="email"
		name={`contacts[${j}].email`}
		on:change={handleChange}
		on:blur={handleChange}
		bind:value={$form.contacts[j].email}
	/>
	{#if $errors?.contacts[j]?.email}
		<div class="error-text">{$errors.contacts[j].email}</div>
	{/if}
</div>

Here’s the component i will create:

<script>
    export let nameAttr;
    export let nameLabel;
    export let bindValue;
    export let errorText;
    export let handleChange;
</script>
<div>
    <label for={nameAttr}>{nameLabel}</label>
    <input
        placeholder={nameLabel}
        name={nameAttr}
        on:change={handleChange}
        on:blur={handleChange}
        bind:value={bindValue}
    />
    {#if errorText}
        <div class="error-text">{errorText}</div>
    {/if}
</div>

… and the ways to call it from the form.svelte page:

<ZInput nameAttr="fullname"
	nameLabel="Full Name"
	bindValue={$form.fullname} 
	errorText={$errors?.fullname} 
	handleChange={handleChange}></ZInput>
<ZInput nameAttr={`contacts[${j}].email`}
	nameLabel="Email"
	bindValue={$form.contacts[j].email} 
	errorText={$errors?.contacts[j]?.email} 
	handleChange={handleChange}></ZInput>

ZRadio – input type=radio in an each loop

The radio buttons are a little more, since we’ll have to supply an array of objects to the component, in a generic way.

The current code looks like this:

<div>
	<label for={`contacts[${j}].product_id`}>Product</label>
	{#each products as p, i}
		<label class="compact">
			<input
				type="radio"
				id={`contacts[${j}].product_id-${p.product_id}`}
				name={`contacts[${j}].product_id`}
				value={p.product_id}
				on:change={handleChange}
				on:blur={handleChange}
			/>
			<span> {p.product_name} [{p.product_id}]</span>
		</label>
	{/each}
	{#if $errors.contacts[j]?.product_id}
		<div class="error-text">{$errors.contacts[j].product_id}</div>
	{/if}
</div>

We’ll extract the following:

  • nameAttr
  • nameLabel
  • itemList [ { id, name, label, value} ]
  • itemValueChecked (if there is a pre-checked item – single choice)
  • errorText
  • handleChange

And we get…

<script>
    export let nameAttr;
    export let nameLabel;
    export let itemList;
    export let itemValueChecked;
    export let errorText;
    export let handleChange;

    function isChecked(checkedValue, itemValue) {
        if(checkedValue === itemValue) {
            return true;
        }
        else {
            return false;
        }
    }
</script>
<div>
    <label for={nameAttr}>{nameLabel}</label>
    {#each itemList as p, i}
        <label class="compact">
            <input
                type="radio"
                id={`${nameAttr}-${p.value}`}
                name={nameAttr}
                value={p.value}
                on:change={handleChange}
                on:blur={handleChange}
                checked={isChecked(itemValueChecked, p.value)}
            />
            <span> {p.label}{#if p.label != p.id}[{p.id}]{/if}</span>
        </label>
    {/each}
    {#if errorText}
        <div class="error-text">{errorText}</div>
    {/if}
</div>

Now the instantiation is a little more complex, as we’ll have to alter or remap the itemList objects to a consistent keys. For simple, non-object array lists, the id, name, label, and value are all the same. But the complex object lists, they are distinct.

The ZRadio component code:

<script>
    export let nameAttr;
    export let nameLabel;
    export let itemList;
    export let itemValueChecked;
    export let errorText;
    export let handleChange;

    function isChecked(checkedValue, itemValue) {
        if(checkedValue === itemValue) {
            return true;
        }
        else {
            return false;
        }
    }
</script>
<div>
    <label for={nameAttr}>{nameLabel}</label>
    {#each itemList as p, i}
        <label class="compact">
            <input
                type="radio"
                id={`${nameAttr}-${p.value}`}
                name={nameAttr}
                value={p.value}
                on:change={handleChange}
                on:blur={handleChange}
                checked={isChecked(itemValueChecked, p.value)}
            />
            <span> {p.label} [{p.id}]</span>
        </label>
    {/each}
    {#if errorText}
        <div class="error-text">{errorText}</div>
    {/if}
</div>

Remapping the item lists:

let prefixOptions = ['Ms.', 'Mr.', 'Dr.'];
let genderOptions = ['F', 'M', 'X'];
let contactTypes = ['friend', 'family', 'aquaintence'];

let products = [
	{ product_id: 101, product_name: 'Boots' },
	{ product_id: 202, product_name: 'Shoes' },
	{ product_id: 333, product_name: 'Jeans' }
];

onMount(() => {
	// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map#using_map_to_reformat_objects_in_an_array

	prefixOptions = simpleRemap(prefixOptions);
	genderOptions = simpleRemap(genderOptions);
	contactTypes = simpleRemap(contactTypes);

	products = products.map((element) => {
		return {
			id: element.product_id,
			name: element.product_name,
			label: element.product_name,
			value: element.product_id,
		};
	});
});

function simpleRemap(itemList) {
	return itemList.map(element => {
		return {
			id: element,
			name: element,
			label: element,
			value: element,
		};
	});
}

Then calling it:

<ZRadio
	nameAttr="prefix"
	nameLabel="Prefix"
	itemList={prefixOptions}
	itemValueChecked="n/a"
	errorText={$errors?.prefix}
	{handleChange}></ZRadio>
<ZRadio
	nameAttr={`contacts[${j}].contacttype`}
	nameLabel="Contact Type"
	itemList={contactTypes}
	itemValueChecked="n/a"
	errorText={$errors.contacts[j]?.contacttype}
	{handleChange}></ZRadio>

<ZRadio
	nameAttr={`contacts[${j}].product_id`}
	nameLabel="Product"
	itemList={products}
	itemValueChecked="n/a"
	errorText={$errors.contacts[j]?.product_id}
	{handleChange}></ZRadio>

Now the functionality should be exactly the same, but the form code is less messy and more readable.

The source code changes are in the same git repo as Part 1, but in a branch “part2”.

https://github.com/nohea/enehana-complex-svelte-form/tree/part2

Svelte Complex Forms with radio buttons, dynamic arrays, and Validation (svelte-forms-lib and yup)

Overview

Building new web apps in 2021 using a Svelte front-end is fun, with more reactivity and less code. Almost any web app will have some kind of form, and it helps to have a basic form builder and validation framework.

In this post, i’ll be exploring the svelte-forms-lib library to create a form, bound to a hierarchical object, and also wired up to a validation object. The form will support dynamically adding/removing items from an array property. It will also support radio buttons, which must be handled differently, since they are multiple <input> elements tied to the same variable.

Building a Complex Form, with svelte-forms-lib

The form i want to build will be a mix of property types:

  • Simple properties, such as ‘fullname’ (text input) and ‘prefix’ (radio button input)
  • A named object property (‘profile’), which will have a subsection for key/value pairs like ‘address’ and ‘gender’
  • A named array property (‘contacts’), which can contain zero or more contacts (with properties ‘name’, ’email’, and ‘contacttype’)

These various properties will have their own validation rules, which we will deal with later. They will also be sent to the backend on form submit, as a single JSON object. Something like this:

{
    fullname: 'Keoki Gonsalves',
    prefix: 'Mr.',
    profile: {
        address: '123 Main St.',
        gender: 'M'
    },
    contacts: [
        {
            contacttype: 'friend',
            name: 'Gina Kekahuna',
            email: 'ginak@example.com',
        },
        {
            contacttype: 'aquaintance',
            name: 'Marlon Waits',
            email: 'mwaits@example.com',
        },
    ]
}

Now that we’ve visualized our data model on the client-side, we can build a form to allow the user to populate that. Our challenge is to manage the slight impedance-mismatch between a form builder library and the object structure. Plus, allowing for an easy to use validation system.

Creating the svelte project, and creating the form with arrays and text inputs

I’ll create a vanilla sveltekit project, but it just needs to be svelte 3:

npm init svelte@next enehana-complex-svelte-form
cd enehana-complex-svelte-form
npm install
npm run dev -- --open

Making a page under /src/routes/form.svelte for this example. I will put as much as possible in this one page for simplicity’s sake, but normally we would split a few things off, as desired.

npm install svelte-forms-lib

We’ll start with a simple <script> section and the html form elements. Our example will be based on the svelte-forms-lib Forms Array example. Let’s just use regular text inputs to start, but do our array which will support multiple contacts on the form.

script section will call createForm() with the initial properties, and return a $form and $errors observable/store for linking the form elements with the JS object.

<script>
	import { createForm } from 'svelte-forms-lib';

	const formProps = {
		initialValues: {
			fullname: '',
			prefix: '',
			profile: {
				address: '',
				gender: ''
			},
			contacts: []
		},
		onSubmit: (values) => {
			console.log('onSubmit (via handleSubmit): ', JSON.stringify(values));
		}
	};

	const { form, errors, state, handleChange, handleSubmit, handleReset } = createForm(formProps);

	const addcontact = () => {
		console.log('addcontact()');
		$form.contacts = $form.contacts.concat({ name: '', email: '', contacttype: '' });
		$errors.contacts = $errors.contacts.concat({ name: '', email: '', contacttype: '' });
	};

	const removecontact = (i) => () => {
		$form.contacts = $form.contacts.filter((u, j) => j !== i);
		$errors.contacts = $errors.contacts.filter((u, j) => j !== i);
	};
</script>

Note there are add() and remove() functions for the contacts array and matching HTML form input sections.

The HTML form we will build out to match, w/css.

<main>
<div>
	<h1>Complex Svelte Form Example</h1>

	<h4>Test Form</h4>
	<form on:submit={handleSubmit}>
		<div>
			<label for="fullname"> Full Name </label>
			<input
				type="text"
				name="fullname"
				bind:value={$form.fullname}
				class=""
				placeholder="Full Name"
				on:change={handleChange}
				on:blur={handleChange}
			/>
		</div>

        <div>
			<label for="profile.address">Profile Address </label>
			<input
				type="text"
				name="profile.address"
				bind:value={$form.profile.address}
				class=""
				placeholder="Profile Address"
				on:change={handleChange}
				on:blur={handleChange}
			/>
		</div>

		<input type="submit" name="submit" value="submit button" />
	</form>
</div>

<div>
	<b>$form: </b>
	<pre>{JSON.stringify($form)}</pre>
</div>
<div>
	<b>$errors: </b>
	<pre>{JSON.stringify($errors)}</pre>
</div>

</main>

<style>
    label {
        display: inline-block;
        width: 200px;
    }

	.error-text {
		color: red;
	}
</style>

This is a simple 2 input form, but you can see the 2-way binding in action:

Now let’s add the dynamic contacts: [] array to the form. We loop using #each on the $form.contacts array, which we start empty. Each time we click “add”, an object is pushed to the array, which is bound to a new form group. Those inputs will be bound to the item of the array, based on their 0-based index value (0, 1, 2, …).

        <h4>Contacts</h4>
        {#each $form.contacts as contact, j}
          <div class="form-group">
            <div>
              <label for={`contacts[${j}].name`}>Name</label>
              <input
                name={`contacts[${j}].name`}
                placeholder="name"
                on:change={handleChange}
                on:blur={handleChange}
                bind:value={$form.contacts[j].name}
              />
            </div>
    
            <div>
                <label for={`contacts[${j}].email`}>Email</label>
                <input
                placeholder="email"
                name={`contacts[${j}].email`}
                on:change={handleChange}
                on:blur={handleChange}
                bind:value={$form.contacts[j].email}
              />
            </div>
    
            {#if $form.contacts.length === j + 1}
                <button type="button" on:click={removecontact(j)}>[- remove last contact]</button>
            {/if}
          </div>
        {/each}
    
        {#if $form.contacts}
            <div>
                <button on:click|preventDefault={addcontact}>[+ add contact]</button>
            </div>
        {/if}

The importance of the name=”” attribute matching the bound js object

We must keep in mind that the HTML form and the $form store is a more “flat” key/value pair data structure, whereas the object is it bound to is a dynamic javascript object, which can easily model hierarchical objects and arrays. This means the way we assign an <input name=””> needs to match the object. Otherwise, our form elements will modify the wrong sections of the object. I had a lot of trouble with this until i figured it out.

The <input> maps by the name=”” attribute, or the id=”” attribute if there is no name. The name/id attribute will be the key in the $form svelte store observable, as well as the matching $errors store.

Examples of the 2-way binding between form and objects:

I try to keep the naming as clear as possible.

formobject
<input name=”fullname” bind:value={$form.fullname} />$form.fullname
<input name=”profile.address” bind:value={$form.profile.address} />$form.profile.address
<input name=”contacts[0].name” bind:value={$form.contacts[0].name} />$form.contacts[0].name
{#each $form.contacts as c, x}
<input name={`contacts[${x}].name`} bind:value={$form.contacts[x].name} />
{/each}
$form.contacts[x].name
{#each $form.contacts as c, x}
{#each contactTypes as ct, y}
<label>
<input type=”radio” name={`contacts[${x}].contacttype`} value={ct} /> {ct}
</label>
{/each}
{/each}
$form.contacts[x].contacttype

It can get a little complicated on the html form side, but i like it clear on the javascript side. Theoretically, the HTML could be wrapped into a svelte component to make the syntax cleaner. Let’s leave that to another day.

Adding in validation using ‘yup’

yup is a form validation library, inspired by Eran Hammer‘s joi.

It seems real simple.

  • npm i yup
  • import * as yup from ‘yup’;
  • define your schema declaratively
  • set it as the validationSchema in the svelte-forms-lib createForm
  • throw in the html $errors next to the form fields, for a visual feedback on invalid data

The validation will run at <form on:submit={handleSubmit}> by svelte-forms-lib, and optionally at the input form element level if you add the on:change={handleChange} and/or on:blur={handleChange} svelte attributes.

Add in a validator schema:

    const validator = yup.object().shape({
        fullname: yup.string().required(),
        prefix: yup.string(),
        profile: yup.object().shape({
            address: yup
                .string()
                .required(),
            gender: yup
                .string()
        }),
        contacts: yup.array().of(
            yup.object().shape({
                contacttype: yup.string(),
                name: yup.string().required(),
                email: yup.string(),
            })
        )
    });

adding a validationSchema property to formProps:

const formProps = {
    ...
    validationSchema: validator,
    ...
}

then adding the error/validation messages near the fields:

{#if $errors.fullname}
	<div class="error-text">{$errors.fullname}</div>
{/if}

and for the deeply-nested fields, i found they often have missing property errors, so i’m using the new javascript optional chaining operator ?.

{#if $errors?.contacts[j]?.name}
  <div class="error-text">{$errors.contacts[j].name}</div>
{/if}

Now we’ve got this working:

Note that onSubmit() doesn’t fire until all the forms pass yup validation.

Handling radio buttons and checkboxes

Radio buttons and checkboxes require special handling. At first i thought i had to wire up my own idiom between svelte-forms-lib and svelte bind:group handler, but it turns out not to be the case.

Sometimes a radio, checkbox, or select drop down will have a list of simple values. In other cases, there could be complex values, in the cases where a list of items is pulled from a databases. There could be a product_id to store, but a product_name to display. I’m going to try examples of each.

The simple examples will be prefixes and genderOptions. We defined them as simple arrays:

const prefixOptions = ['Ms.', 'Mr.', 'Dr.'];
const genderOptions = ['F', 'M', 'X'];
const contactTypes = ['friend', 'family', 'aquaintence'];

The complex example:

    const products = [
        { product_id: 101, product_name: "Boots", },
        { product_id: 202, product_name: "Shoes", },
        { product_id: 333, product_name: "Jeans", },
    ];

For ‘prefix’, we have a similar label, but instead of one <input>, we get one for each option. So we loop thru the options using an {#each} loop, being careful to:

  • set all name=”” attributes to the same input name
  • set the value=”” to the actual value to store in the variable
  • use the on:change={handleChange} handler
<div>
	<label for="prefix"> Prefix </label>
	{#each prefixOptions as pre, i}
		<label class="compact">
			<input id={`prefix-${pre}`} 
			name="prefix" 
			value={pre}
			type="radio" 
			on:change={handleChange}
			on:blur={handleChange}
			/>
		<span> {pre} </span>
		</label>
	{/each}
	{#if $errors.prefix}
		<div class="error-text">{$errors.prefix}</div>
	{/if}
</div>

For $form.profile.gender, it is almost identical, but the naming must follow one level deeper:

<div>
	<label for="profile.gender"> Profile Gender</label>
	{#each genderOptions as g, i}
		<label class="compact">
			<input id={`prefix-${g}`} 
			name="profile.gender" 
			value={g}
			type="radio" 
			on:change={handleChange}
			on:blur={handleChange}
			/>
		<span> {g} </span>
		</label>
	{/each}
	{#if $errors.profile?.gender}
		<div class="error-text">{$errors.profile.gender}</div>
	{/if}
</div>

And with Contact Type, we need to include the array indexer in the name=”” attribute, so we don’t stomp on values from other array items. It is already inside another {#each} loop, iterating over $form.contacts

<div>
    <label for={`contacts[${j}].contacttype`}>Contact Type</label>
    {#each contactTypes as ct, i}
        <label class="compact">
            <input 
            type="radio" 
            id={`contacts[${j}].contacttype-${ct}`} 
            name={`contacts[${j}].contacttype`}
            value={ct}
            on:change={handleChange}
            on:blur={handleChange}
            />
        <span> {ct} </span>
        </label>
    {/each}
    {#if $errors.contacts[j]?.contacttype}
        <div class="error-text">{$errors.contacts[j].contacttype}</div>
    {/if}
</div>

Finally, let’s combine the array radio with a complex list of items: the ID will be the value, but the display will be a name or description

<div>
	<label for={`contacts[${j}].product_id`}>Product</label>
	{#each products as p, i}
		<label class="compact">
			<input 
			type="radio" 
			id={`contacts[${j}].product_id-${p.product_id}`} 
			name={`contacts[${j}].product_id`}
			value={p.product_id}
			on:change={handleChange}
			on:blur={handleChange}
			/>
		<span> {p.product_name} [{p.product_id}]</span>
		</label>
	{/each}
	{#if $errors.contacts[j]?.product_id}
		<div class="error-text">{$errors.contacts[j].product_id}</div>
	{/if}
</div>

Conclusion

My takeaway is that based on this test of more complex form building and validation using svelte, i’m now confident i could build larger web apps the way i expect — with validation and dynamic forms, including arrays.

I’d like to improve and refactor the examples into components— either the ones provided, or making my own.

References

https://svelte-forms-lib-sapper-docs.vercel.app/array

Nefe James – Top form validation libraries in Svelte

Source code at github

https://github.com/nohea/enehana-complex-svelte-form part 1

How to connect Hasura GraphQL real-time Subscription to a reactive Svelte frontend using RxJS and the new graphql-ws Web Socket protocol+library

By Raul Nohea Goodness
https://twitter.com/rngoodness
November 2021

Overview

I am in the middle of my about once or twice-a-decade process of reevaluating my entire web software development tools and approaches. I’m using a number of great new tools, but a new little JS lib i’m starting to use to tie them all together, hopefully in a resilient way: graphql-ws

The target audience for this post is a web developer using a modern GraphQL backend (Hasura in this case) and a modern reactive javascript/html front-end (in this example, Svelte). 

This post is about the reasons for my tech stack choices, and how to use graphql-ws to elegantly tie them together. 

Software Stack Curation

What is Hasura? Why use it?

Hasura, in my mind, is a revolutionary new backend data server. It sits in front of a database (PostgreSQL or others), and provides:

  • Instant GraphQL APIs (which are typed)
  • Configurable Authorization of resources, integrated at the SQL composition level
  • Bring your own Authentication/Authorization provider (using JWTs or not), such as NHost, Auth0, Firebase, etc. 
  • Integrate with other GraphQL sources
  • Integrate hooks with serverless functions/lambda
  • Open Source (self-host or cloud service)
  • Local CLI for developers

This can eliminate extensive hand-coding of backend REST APIs, with the custom cross-cutting concerns, like Auth. Also replaces the need for OR/M-style data access in backend code. 

What is GraphQL? Why use it?

Now, this was my question a couple years ago, until i saw Hasura v1. Now i can answer it. 

From graphql.org

A query language for your API
GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools.

In slightly more normal coder-speak, it is a defacto standard for querying and mutating (insert/update/delete) a data source over the web, sending a GQL statement, executing it, and receiving a response in JSON. 

GraphQL consoles are “aware” of the underlying database types, which makes it easy to:

  • Compose queries in a console like “graphiql” and test them
  • Then copy/paste your GQL into your Javascript client code editor, for run-time execution

Arguably, this is less work than hand-coding the SQL or ORM code into your REST endpoint code. The JSON response comes for free. GraphQL also makes it easy to merge multiple data sources into a single JSON response. 

What is Apollo Client? Why use it, and why would i not use it?

Apollo is a GraphQL client and server library. It is popular and there are many code examples for developers available. Since i am using Hasura i don’t need the Apollo Server, but i could use the Apollo Client to access my backend. 

My initial tests worked with it. However the Apollo Client also has its own state-management system for caching gql queries and responses. It seemed like an overkill solution for my uses. I’m sure it works for other projects, but since the new concept count (to learn) in this case is already high, i opted to not use it. 

Instead i started using a more lightweight library: https://graphql.org/graphql-js/graphql/

This worked good and was simple to understand, but only for queries and mutations, not subscriptions. 

For gql subscriptions, there was a different library: apollographql / subscriptions-transport-ws . It is for graphql subscriptions over web sockets. We would want this in the case of a web UX which listens for changes in the underlying data, and reactively updates when it changes on the server. 

What is graphql-ws? Why use it instead of subscriptions-transport-ws? 

subscriptions-transport-ws does work, but there are 3 reasons not to use it:

  • Bifurcated code – you have to use one lib for gql queries+mutations, and another for subscriptions
  • graphql-ws implements a more standard GraphQL over WebSocket Protocol, using ping/pong messages, instead of subscriptions-transport-ws GCL_* messages. 
  • Apparently subscriptions-transport-ws is no longer actively maintained by the original developers, and they recommend using graphql-ws on their project page.

Note that Hasura added support for graphql-ws protocol as of v2.0.8.

What are graphql subscriptions?

From the Hasura docs:

Subscriptions – Realtime updates

The GraphQL specification allows for something called subscriptions that are like GraphQL queries but instead of returning data in one read, you get data pushed from the server.

This is useful for your app to subscribe to “events” or “live results” from the backend, while allowing you to control the “shape” of the event from your app.

GraphQL subscriptions are a critical component of adding realtime or reactive features to your apps easily. GraphQL clients and servers that support subscriptions allow you to build great experiences without having to deal with websocket code!

Put another way, our front-end UX can “listen” for changes on the backend, and the backend will send the changes to the frontend over the web socket in real time. The “reactive” frontend can instantly re-render the update to the user. 

Not all graphql queries require using a subscription, but if we do use them, coding them will be much simpler to write and maintain. 

What is Svelte? Why use it?

Svelte is a Javascript front-end reactive framework (not unlike React), but it is succinct and performant, and implemented as a compiler (to JS). Plus, it is fun to learn and code in. I’m talking 1999- era fun 😊

I recommend watching Rich Harris’ talk: Rethinking Reactivity

You can use a different frontend framework. But Svelte makes it easy due to svelte “stores” implementing the observable contract– the subscribe() method. Components will reactively update if the underlying object being observed changes. 

What are Javascript Observables? RxJS?

RxJS is a library for reactive programming using Observables, to make it easier to compose asynchronous or callback-based code. 

We don’t need RxJS to use observables, but it is a popular library. I used it with Angular in the past, and one of the simplest graphql-ws examples uses it, so i am too. 

In short, in Javascript you call an observable’s subscribe() method to listen for/handle updates in the observable’s value. 

The wire-up: two-way reactive front-end to backend using JS Observables + GraphQL Subscriptions over Web Sockets

The idea here is to render the rapidly-changing data in an HTML component for the user to just watch updates, without having to do anything. 

Design – Focus-group input slider

This proof-of-concept will be a slider for use in a “focus group”. A group of participants get in a room and watch a video or debate, and “dial” in real-time their opinion (positive or negative) as things are being said. This example will just be a single person’s input being displayed or charted. 

  • The data captured will include: focus group id (text), username, rating (integer – 0 to 100), and datetime of event. 
  • UI will include:
    • A start/stop button, to start recording rating records, in 1 second increments. 
    • A slider, which goes from 0 (negative/disagree) to 100 (positive/agree), default setting is 50 (neutral)
  • A grid/table will display the last 10 records recorded in real-time (implemented as a graphql subscription). 
  • Optional: implement a chart component which updates in real-time from the data set. 

Diagram

Code

Setup

npm init svelte@next fgslider
cd fgslider
code .

PostgreSQL

I want the table to look like this:

create table ratingtick (
   id serial,
   focusgroup text not null,
   username text not null,
   rating integer not null,
   tick_ts timestamp with time zone not null default current_timestamp
);
 
-- insert into ratingtick(focusgroup, username, rating) values ('pepsi ad', 'ekolu', 50);
-- insert into ratingtick(focusgroup, username, rating) values ('pepsi ad', 'ekolu', 65);
-- insert into ratingtick(focusgroup, username, rating) values ('pepsi ad', 'ekolu', 21);

In this case, i’m going to do it on my local machine. I’m also going to create the Hasura instance locally using hasura-cli. Of course, you can do this on your local infrastructure or your own servers or cloud provider, or the specialized NHost.io

Hasura

I’m going to create a Hasura container locally, which will also have a PostgreSQL v12 instance. 

sudo apt install docker-compose docker

docker-compose up -d

If you get a problem, just tweak docker-compose.yml. I changed the port from 8080:8080 to 8087:8080

Connect to the Hasura web console:
http://localhost:8087

Connect the Hasura container instance to the Postgresql container instance:

Grab the database URL from docker-compose.yml and connect the database:

You will now see ‘pgcontainer’ in the databases list. 

With Hasura, you can either create the Postgres schema first, then tell Hasura to scan the schema. Or create the schema in the Hasura console, which will execute the DDL on Postgres. Pick one or the other. 

For this project, we’ll skip permissions, or more accurately, we’ll configure a ‘public’ role on the table, and allow select/insert/update/delete permissions. 

Note: i had to add HASURA_GRAPHQL_UNAUTHORIZED_ROLE: public to the environment: section of docker-compose.yml and run “docker-compose up -d” to make it reload with the setting change, to treat anonymous requests as ‘public’ role (no need for x-hasura-role header). 

Let’s now test GraphQL queries in “GraphIQL” tool. We should be able to set the x-hasura-role  header to ‘public’ and still query/mutate. Setting the role header requires Hasura to evaluate the authorization according to that role. (note i did have problems getting the role header to work, so i instead made ‘public’ the default anonymous role).

We should also be able to insert via a mutation:

mutation MyMutation {
  insert_ratingtick_one(object: {focusgroup: "pepsi ad", username: "ekolu", rating: 50}) {
    id
  }
}

Response:

{
  "data": {
    "insert_ratingtick_one": {
      "id": 1
    }
  }
}

That means it inserted and returned the ‘id’ primary key of 1. 

After inserting a few, we can query again:

{
  "data": {
    "ratingtick": [
      {
        "id": 1,
        "focusgroup": "pepsi ad",
        "username": "ekolu",
        "rating": 50,
        "tick_ts": "2021-11-16T22:56:07.094606+00:00"
      },
      {
        "id": 2,
        "focusgroup": "pepsi ad",
        "username": "ekolu",
        "rating": 45,
        "tick_ts": "2021-11-16T22:57:56.323054+00:00"
      },
      {
        "id": 3,
        "focusgroup": "pepsi ad",
        "username": "ekolu",
        "rating": 98,
        "tick_ts": "2021-11-16T22:58:01.047135+00:00"
      },
      {
        "id": 4,
        "focusgroup": "pepsi ad",
        "username": "ekolu",
        "rating": 96,
        "tick_ts": "2021-11-16T22:58:09.495674+00:00"
      },
      {
        "id": 5,
        "focusgroup": "pepsi ad",
        "username": "ekolu",
        "rating": 43,
        "tick_ts": "2021-11-16T22:58:17.550324+00:00"
      },
      {
        "id": 6,
        "focusgroup": "pepsi ad",
        "username": "ekolu",
        "rating": 23,
        "tick_ts": "2021-11-16T22:58:25.547917+00:00"
      }
    ]
  }
}

Finally, let’s test the subscription. We should be able to open the insert mutation in one window, and see the subscription update in real time in the second window. 

Good. At this point, i’m confident all is working on the Hasura end. Time to work on the front-end code. 

Svelte + graphql-ws

Please note that although i am using Svelte with graphql-ws , you can use any JS framework, or vanilla JS. 

Remember, we created this directory as a sveltekit project, so now we’ll build on it. We do need to “npm install” to install the node dependencies. Then we can “npm run dev” which will run the dev http server on localhost:3000

  • Create a new /slider route as src/routes/slider/index.svelte
  • Add form inputs, and a slider widget
  • Add a display grid which will display the last 10 tick records

SvelteKit uses Vite for modern ES6 module builds, which uses dotenv-style .env, but with the VITE_* prefix. So we create a .env file with entry like so:

VITE_TEST="this is a test env"
VITE_HASURA_GRAPHQL_URL=ws://localhost:8087/v1/graphql

Note: you must change the URI protocol from http://localhost:8087/v1/graphql to ws://localhost:8087/v1/graphql , in order to use graphql-ws. It is not normal http, it is web sockets (ws://) or ws secure (wss://). Otherwise, you get an error: [Uncaught (in promise) DOMException: An invalid or illegal string was specified client.mjs:140:12]

Then you can refer to them in your app via the import.meta.env.* namespace (src/routing/index.svelte):

Now let’s get into the “fish and poi” a/k/a “meat and potatoes” section, the src/routes/slider/index.svelte page. 

First, the start/stop button, form elements and slider widget. Keeping it simple, 

I will install a custom svelte slider component:

npm install svelte-range-slider-pips --save-dev

Also installing rxjs, for the timer() and later for wrapping the graphql-ws handle. 

npm install rxjs

The first version here is basically a svelte app only, not using any backend yet:

<script>
import { text } from "svelte/internal";
import RangeSlider from "svelte-range-slider-pips";
import { timer } from 'rxjs';
 
let runningTicks = false;
let focusGroupName = "pepsi commercial";
let userName = "ekolu";
let sliderValues = [50]; // default
let tickLog = "";
 
let timerObservable;
let timerSub;
 
function timerStart() {
   runningTicks = true;
   timerObservable = timer(1000, 1000);
 
   timerSub = timerObservable.subscribe(val => {
       tickLog += `tick ${val}... `;
   });
}
 
function timerStop() {
   timerSub.unsubscribe();
   runningTicks = false;
}
 
</script>
 
<h1>Slider</h1>
<p>
   enter your focus group, name and click 'start'.
</p>
<p>
   Once it starts, move the slider depending on how much you
   agree/disagree with the video.
</p>
 
<form>
<label for="focusgroup">focus group: </label><input type="text" name="focusgroup" bind:value={focusGroupName} />
<label for="username">username: </label><input type="text" name="focusgroup" bind:value={userName} />
 
<label for="ratingslider">rating slider (0 to 100): </label>
 
<RangeSlider name="ratingslider" min={0} max={100} bind:values={sliderValues} pips all='label' />
<div>0 = bad/disagree, 50 = neutral, 100 = good/agree</div>
<div>slider Value: {sliderValues[0]}</div>
 
<button disabled={runningTicks} on:click|preventDefault={timerStart}>Start</button>
<button disabled={!runningTicks} on:click|preventDefault={timerStop}>Stop</button>
</form>
<div>
   Tick output: {tickLog}
</div>
 
<div>
   <a href="/">Home</a>
</div>

I got a number of things working together here:

  • Variables bound to UI components
  • A slider component which will have values from 0 to 100, bound to variable
  • An rxjs timer(), which executes a callback every second, bound to the start/stop buttons

Now i’m ready to hook up the graphql mutation and subscription. 

npm install graphql-ws

I’m going to create src/lib/graphql-ws.js to manage the client setup and subscription creation. 

import { createClient } from 'graphql-ws';
import { observable, Observable } from 'rxjs';

export function createGQLWSClient(url) {
    // console.log(`createGQLWSClient(${url})`);
    return createClient({
        url: url,
    });
}

export async function createQuery(client, gql, variables) {
    // query
    return await new Promise((resolve, reject) => {
        let result;
        client.subscribe(
            {
                query: gql,
                variables: variables
            },
            {
                next: (data) => (result = data),
                error: reject,
                complete: () => resolve(result)
            }
        );
    });
}

export async function createMutation(client, gql, variables) {
    // same as query
    return createQuery(client, gql, variables);
}

export function createSubscription(client, gql, variables) {
    // hasura subscription
    // console.log("createSubscription()");
    const operation = {
        query: gql,
        variables: variables,
    };
    const rxjsobservable = toObservable(client, operation);
    // console.log("rxjsobservable: ", rxjsobservable);
    return rxjsobservable;
}

// wrap up the graphql-ws subscription in an observable
function toObservable(client, operation) {
    // console.log("toObservable()");
    // the graphql-ws subscription may be cleaned up here, 
    // not sure about the RxJs Observable
    // trying to make it more like the docs, w/custom unsubscribe() on subscription object
    // https://rxjs.dev/guide/observable
    return new Observable(function subscribe(subscriber) {
        client.subscribe(operation, {
            next: (data) => subscriber.next(data),
            error: (err) => subscriber.error(err),
            complete: () => subscriber.complete()
        });

        // Provide a way of canceling and disposing resources
        return function unsubscribe() {
            console.log("unsubscribe()");
        };
    });
}

Now we are going to:

  • setup the client in the index.svelte onMount() handler, 
  • execute createSubscription() in the onMount() handler and bind to a new grid/table component
  • execute createMutation() on every tick with the current values
// browser-only code
onMount(async () => {
	// setup the client in the index.svelte onMount() handler
	gqlwsClient = createGQLWSClient(import.meta.env.VITE_HASURA_GRAPHQL_URL);

	// execute createSubscription() in the onMount() handler

	// and bind to a new grid/table component
	// src/components/TopTicks.svelte
	const gql = `subscription MySubscription($limit:Int) {
ratingtick(order_by: {id: desc}, limit: $limit) {
id
focusgroup
username
rating
tick_ts
}
}`;
	const variables = { limit: 5 }; // how many to display
	const rxjsobservable = createSubscription(
		gqlwsClient,
		gql,
		variables
	);
	// const subscription = rxjsobservable.subscribe(subscriber => {
	// 	console.log('subscriber: ', subscriber);
	// });
	// console.log('subscription: ', subscription);
	// gqlwsSubscriptions.push(subscription);
	gqlwsObservable = rxjsobservable;
});

Timer start

   function timerStart() {
       runningTicks = true;
       timerObservable = timer(1000, 1000);
 
       timerSub = timerObservable.subscribe((val) => {
           tickLog += `tick ${val}... `;
 
           // execute createMutation() on every tick with the current values
           submitLatestRatingTick(gqlwsClient);
       });
   }

Functions to do the work:

   function submitLatestRatingTick(client) {
       const gql = `mutation MyMutation($focusgroup:String, $username:String, $rating:Int) {
 insert_ratingtick_one(object: {focusgroup: $focusgroup, username: $username,
   rating: $rating}) {
   id
 }
}
`;
       const variables = buildRatingTick();
 
       createMutation(client, gql, variables);
   }
 
   function buildRatingTick() {
       return {
           focusgroup: focusGroupName,
           username: userName,
           rating: sliderValues[0]
       };
   }

Note, we can test the gql in GraphIQL and copy/paste into the JS template strings, also using the variable syntax. 

Update: One more thing, i forgot to include my <TopTicks> component code:

<script>
    export let observable;
</script>
{#if $observable}
<h3>Top Ticks</h3>
<table>
    <thead>
        <tr>
            <th>id</th>
            <th>focus group</th>
            <th>user</th>
            <th>rating</th>
            <th>tick ts</th>
        </tr>
    </thead>
    <tbody>
        {#each $observable.data.ratingtick as item}
        <tr>
            <td>{item.id}</td>
            <td>{item.focusgroup}</td>
            <td>{item.username}</td>
            <td>{item.rating}</td>
            <td>{item.tick_ts}</td>
        </tr>
        {/each}

    </tbody>
</table>
{/if}

We pass the gqlwsObservable to the svelte component in a prop:

<TopTicks observable={gqlwsObservable} />

If that all works, we will have a sweet reactive graphql-ws app. 

Got it all working now! 😎

Animated GIF version:

Connecting it to a reactive chart is left as an exercise for the reader. 

github

find the source for this app here:
https://github.com/nohea/enehana-fgslider

References

graphql-ws: GraphQL over WebSocket Protocol compliant server and client.
https://github.com/enisdenjo/graphql-ws

SpinSpire: live code: Svelte app showing realtime Postgres data changes (GraphQL subscriptions)

Hasura – local docker install

Svelte

Partial Updates with HTTP PATCH using ServiceStack.net and the JSON Patch format (RFC 6902)

I have been looking into implementing partial updates using the HTTP PATCH method using ServiceStack.net and the JSON Patch format (RFC 6902)

This is of interest since many updates do not neatly match the PUT method, which often is used for full entity updates (all properties). PATCH is intended to do one or more partial updates. There are a few blogs describing the use cases.

I’ve been happy using ServiceStack the way it was designed – RESTful, simple, using Message Based designs.

I could implement PATCH using my own message format – that is easy to do. Usually it would be the actual DTO properties, plus a list of fields which are actually going to be updated. You wouldn’t update all fields, and you don’t want to only update non-null properties, since sometimes “null” is a valid value for a property (it would be impossible to set a property to null from non-null).

In my opinion, using JSON Patch for the Request body has pros and cons.
Pros:

  • is an official RFC
  • covers a lot of use cases

Cons:

  • very generic, so we lose some of the benefit of strong typing
  • doesn’t have a slot for the Id of a resource when calling PATCH /employees/{Id}
    • doing this the “JSON Patch way” would be { “op”: “replace”, “path”: “/employees/123/title”, “value”: “Administrative Assistant” } , but that wastes the value of having it on the routing path.

JSON Patch supports a handful of operations: “add”, “remove”, “replace”, “move”, “copy”, “test”. I will focus on the simple “replace” op, since it easily maps to replacing a property on a DTO (or field in a table record).

The canonical example looks like this:

PATCH /my/data HTTP/1.1
Host: example.org
Content-Length: 55
Content-Type: application/json-patch+json
If-Match: "abc123"

[
    { "op": "replace", "path": "/a/b/c", "value": 42 }
]

I’m going to ignore the If-Match: / ETag: headers for now. Those will be useful if you want to tell the server to only apply your changes if the resource still matches your “If-Match” header (no changes in the meantime). “That exercise is left to the reader.”

Let’s say we have a more practical example:

  • an Employee class, backed by an [Employee] table, accessed by OrmLite
  • an EmployeeService class, implementing the PATCH method
  • the Request DTO to the Patch() method aligns to the JSON Patch structure

The Employee class would simply look like this (with routing for basic CRUD):

[Route("/employees", "GET,POST")]
[Route("/employees/{Id}", "GET,PUT")]
public class Employee
{
    public long Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public string Title { get; set; }
    public int? CubicleNo { get; set; }
    public DateTime StartDate { get; set; }
    public float Longitude { get; set; }
    public float Latitude { get; set; }
}

Now the shape of JSON Patch replace ops would look like this:

PATCH /employees/123 HTTP/1.1
Host: example.org
Content-Type: application/json

[
    { "op": "replace", "path": "/title", "value": "Junior Developer" },
    { "op": "replace", "path": "/cubicleno", "value": 23 },
    { "op": "replace", "path": "/startdate", "value": "2013-06-02T09:34:29-04:00" }
]

The path is the property name in this case, and the value is what to update to.

And yes, i also know i am sending Content-Type: application/json instead of Content-Type: application/json-patch+json . We’ll have to get into custom content type support later too.

Now, sending a generic data structure as the Request DTO to a specific resource ID doesn’t cleanly map to the ServiceStack style, because:

  • each Request DTO should be a unique class and route
  • there is not a field in the Request for the ID of the entity

The simple way to map the JSON to a C# class would define an “op” element class, and have a List<T> of them, like so:

public class JsonPatchElement
{
    public string op { get; set; } // "add", "remove", "replace", "move", "copy" or "test"
    public string path { get; set; }
    public string value { get; set; }
}

We create a unique Request DTO so we can route to the Patch() service method.

[Route("/employees/{Id}", "PATCH")]
public class EmployeePatch : List<JsonPatchElement>
{
}

But how do we get the #$%&& Id from the route?? This code throws RequestBindingException! But i can’t change the shape of the PATCH request body from a JSON array [].
The answer was staring me in the face: just add it to the DTO class definition, and ServiceStack will map to it. I was forgetting the C# class doesn’t have to be the same shape as the JSON.

[Route("/employees/{Id}", "PATCH")]
public class EmployeePatch : List<JsonPatchElement>
{
    public long Id { get; set; }
}

Think of this class as a List<T> with an additional Id property.

When the method is called, the JSON Patch array is mapped and the Id is copied from the route {Id}.

public object Patch(EmployeePatch dto)
{
    // dto.Id == 123
    // dto[0].path == "/title"
    // dto[0].value == "Joe"
    // dto[1].path == "/cubicleno"
    // dto[1].value == "23"

The only wrinkle is all the JSON values come in as C# string, even if they are numeric or Date types. At least you will know the strong typing from your C# class, so you know what to convert to.

My full Patch() method is below– note the partial update code uses reflection to update properties of the same name, and does primitive type checking for parsing the string values from the request DTO.

public object Patch(EmployeePatch dto)
{
    // partial updates

    // get from persistent data store by id from routing path
    var emp = Repository.GetById(dto.Id);

    if (emp != null)
    {
        // read from request dto properties
        var properties = emp.GetType().GetProperties();

        // update values which are specified to update only
        foreach (var op in dto)
        {
            string fieldName = op.path.Replace("/", "").ToLower(); // assume leading /slash only for example

            // patch field is in type
            if (properties.ToList().Where(x => x.Name.ToLower() == fieldName).Count() > 0)
            {
                var persistentProperty = properties.ToList().Where(x => x.Name.ToLower() == fieldName).First();

                // update property on persistent object
                // i'm sure this can be improved, but you get the idea...
                if (persistentProperty.PropertyType == typeof(string))
                {
                    persistentProperty.SetValue(emp, op.value, null);
                }
                else if (persistentProperty.PropertyType == typeof(int))
                {
                    int valInt = 0;
                    if (Int32.TryParse(op.value, out valInt))
                    {
                        persistentProperty.SetValue(emp, valInt, null);
                    }
                }
                else if (persistentProperty.PropertyType == typeof(int?))
                {
                    int valInt = 0;
                    if (op.value == null)
                    {
                        persistentProperty.SetValue(emp, null, null);
                    }
                    else if (Int32.TryParse(op.value, out valInt))
                    {
                        persistentProperty.SetValue(emp, valInt, null);
                    }
                }
                else if (persistentProperty.PropertyType == typeof(DateTime))
                {
                    DateTime valDt = default(DateTime);
                    if (DateTime.TryParse(op.value, out valDt))
                    {
                        persistentProperty.SetValue(emp, valDt, null);
                    }
                }

            }
        }

        // update
        Repository.Store(emp);

    }

    // return HTTP Code and Location: header for the new resource
    // 204 No Content; The request was processed successfully, but no response body is needed.
    return new HttpResult()
    {
        StatusCode = HttpStatusCode.NoContent,
        Location = base.Request.AbsoluteUri,
        Headers = {
            // allow jquery ajax in firefox to read the Location header - CORS
            { "Access-Control-Expose-Headers", "Location" },
        }
    };
}

For an example of calling this from the strongly-typed ServiceStack rest client, my integration test looks like this:

[Fact]
public void Test_PATCH_PASS()
{
    var restClient = new JsonServiceClient(serviceUrl);

    // dummy data
    var newemp1 = new Employee()
    {
        Id = 123,
        Name = "Kimo",
        StartDate = new DateTime(2015, 7, 2),
        CubicleNo = 4234,
        Email = "test1@example.com",
    };
    restClient.Post<object>("/employees", newemp1);

    var emps = restClient.Get<List<Employee>>("/employees");

    var emp = emps.First();

    var empPatch = new Operations.EmployeePatch();
    empPatch.Add(new Operations.JsonPatchElement()
    {
        op = "replace",
        path = "/title",
        value = "Kahuna Laau Lapaau",
    });

    empPatch.Add(new Operations.JsonPatchElement()
    {
        op = "replace",
        path = "/cubicleno",
        value = "32",
    });

    restClient.Patch<object>(string.Format("/employees/{0}", emp.Id), empPatch);

    var empAfterPatch = restClient.Get<Employee>(string.Format("/employees/{0}", emp.Id));

    Assert.NotNull(empAfterPatch);
    // patched
    Assert.Equal("Kahuna Laau Lapaau", empAfterPatch.Title);
    Assert.Equal("32", empAfterPatch.CubicleNo.ToString());
    // unpatched
    Assert.Equal("test1@example.com", empAfterPatch.Email);
}

I am uploading this code to github a full working Visual Studio 2013 project, including xUnit.net tests.

I hope this has been useful to demonstrate the flexibility of using ServiceStack and C# to implement the HTTP PATCH method using JSON Patch (RFC 6902) over the wire.

Update: i refactored the code so that any object can have it’s properties “patched” from a JsonPatchRequest DTO by using an extension method populateFromJsonPatch().

public object Patch(EmployeePatch dto)
{
    // partial updates
    // get from persistent data store by id from routing path
    var emp = Repository.GetById(dto.Id);

    if (emp != null)
    {
        // update values which are specified to update only
        emp.populateFromJsonPatch(dto);

        // update
        Repository.Store(emp);

 

 

Using Handlebars.js templates as precompiled JS files

I’ve previously used Handlebars templates in projects, but only in the simple ways– i defined a <script> block as inline html templates, and used in my js code.

However, i have a project where i need all the code, including html templates, as js files.
Luckily Handlebars can do this, but we’ll need to set up the proper node-based build environment to do so.

  • node.js
  • gulp task runner
  • bower for flat package management
  • handlebars for templates

The templates will get “precompiled” by gulp, resulting in a pure js file to include in the html page. Then we’ll be able to code in HTML, but deploy as JS.

First i create a new empty ASP.NET Web project in Visual Studio. I’ll call it: HandlebarsTest. Note that almost none of this is Visual Studio-specific, so 95% is applicable to any other development environment.

Next, i will set up Gulp and Bower, similar to how i did it in my 2 prior posts:

I will create the gulpfile.js like so (we’ll add it it):

var gulp = require('gulp');

gulp.task('default', ['scripts'], function() {

});

gulp.task('scripts', function() {
});

Open the node command prompt, and change to the new directory

cd HandlebarsTest\HandlebarsTest
npm init
npm install -g gulp
npm install gulp --save-dev
npm install gulp-uglify --save-dev
npm install gulp-concat --save-dev
npm install gulp-wrap --save-dev
npm install gulp-declare --save-dev

I will create the .bowerrc file like so:

{
    "directory": "js/lib"
}

OK, now for some handlebars stuff. One thing to understand is we need to do handlebars stuff at build/compile time AND at runtime. That means:

  • the precompilation will be run by gulp during build time (install gulp-handlebars using npm), and
  • the web browser will execute the templates with the handlebars-runtime library (install to the project using Bower)
npm install gulp-handlebars --global
npm install gulp-handlebars --save-dev

Bower (client-side) packages

I will use Bower to install the client side libs: handlebars, jquery, etc. First, create the bower.json file.

bower init

Next, start installing!

bower install jquery
bower install handlebars

Those files get installed to /js/lib/* , per my .bowerrc file. Now we can reference them in scripts, or use them for js bundles.

HTML, Javascript, and Handlebars templates together.

My use-case is to:

  1. Have a static HTML page
  2. Include a script tag which loads a single JS file
  3. The single JS file will load/contain the libraries AND the main execution code
  4. the main execution code will render a DIV element which renders a Handlebars template with an object.

HTML page just includes a single JS , which will be built:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Handlebars Test</title>
    <script type="text/javascript">
    (function() {
        function async_load(){
            var cb = 'cb=' +(new Date).getTime();

            var rmist = document.createElement('script');
            rmist.type = 'text/javascript';
            rmist.async = true;
            rmist.src = '../js/dist/bundle.js?' + cb;
            var x = document.getElementsByTagName('script')[0];
            x.parentNode.insertBefore(rmist, x);
        }
        if (window.attachEvent)
            window.attachEvent('onload', async_load);
        else
            window.addEventListener('load', async_load, false);
    }());
    </script>
</head>
<body>

    <h1>Handlebars Test</h1>

    <p id="main-content">
        There will be a dynamic element added after this paragraph.
    </p>
    <p id="dynamic-content"></p>

</body>
</html>

Handlebars templates will be in /templates/*.hbs . Here’s an example, i’m calling /templates/hellotemplate.hbs:

<div class="hello" style="border: 1px solid red;">
    <h1>{{title}}</h1>
    <div class="body">
        Hello, {{name}}! I'm a template. 
    </div>
</div>

Javascript will be in the /js/app/app.js and the other libraries

Here, i’m taking direction from https://github.com/wycats/handlebars.js#precompiling-templates

gulp-handlebars handles the precompilation. We will run the ‘gulp’ build process to precompile hbs templates to js later.

The app.js code will need to render the precompiled template with the data object, and add to the DOM somehow (using jQuery in this case).

"use strict";
var data = { title: 'This Form', name: 'Joey' };
var html = MyApp.templates.hellotemplate(data);
// console.log(html);

$(document).ready(function () {
    $('#dynamic-content').html(html);
});

Precompiling the templates and using them

I will modify the gulpfile.js to add a task for template compilation. This is my final version:

var gulp = require('gulp');
var uglify = require('gulp-uglify');
var concat = require('gulp-concat');

gulp.task('default', ['templates','scripts'], function () {

});

var handlebars = require('gulp-handlebars');
var wrap = require('gulp-wrap');
var declare = require('gulp-declare');
var concat = require('gulp-concat');

gulp.task('templates', function () {
    gulp.src('templates/*.hbs')
      .pipe(handlebars())
      .pipe(wrap('Handlebars.template(<%= contents %>)'))
      .pipe(declare({
          namespace: 'MyApp.templates',
          noRedeclare: true, // Avoid duplicate declarations
      }))
      .pipe(concat('templates.js'))
      .pipe(gulp.dest('js/dist'));
});

gulp.task('scripts', function () {
    return gulp.src(['js/lib/jquery/dist/jquery.js', 'js/lib/handlebars/handlebars.runtime.js', 'js/dist/templates.js', 'js/app/**/*.js'])
      .pipe(concat('bundle.js'))
      .pipe(uglify())
      .pipe(gulp.dest('js/dist/'));
});

The key section is the ‘templates’ task. Translating:

  • read all *.hbs templates
  • process thru handlebars() precomilation
  • setting the namespace MyApp.templates
  • output to a single JS file js/dist/templates.js

The scripts task combines all the JS files to one bundle.js. However, i had some trouble debugging the code, so i first ran the JS without a bundle. I changed the html to use traditional javascript references instead of the bundle.js:

<head>
    <title>Handlebars Test</title>
    <script src="../js/lib/jquery/dist/jquery.min.js"></script>
    <script src="../js/lib/handlebars/handlebars.runtime.min.js"></script>
    <script src="../js/dist/templates.js"></script>
    <script src="../js/app/app.js"></script>
</head>

The load order is important– libraries, then templates, then the main app code. After fixing bugs, i get the desired HTML output in page:

handlebars-test-html-nobundle

Note the multiple GET requests. But it functionally is working.

Run the bundled version

Now that the JS code runs the templates with jQuery OK, we can remove the multiple script references and switch to the single bundle.js script.

Don’t forget to execute the ‘gulp’ build again (on the command line or via visual studio). Looking at the gulp ‘script’ task, note the order of the bundling concatenation needs to be the same order as the <script> tag includes would be in the above example. Otherwise, things wlil get out of order.

gulp.task('scripts', function () {
    return gulp.src(['js/lib/jquery/dist/jquery.js', 'js/lib/handlebars/handlebars.runtime.js', 'js/dist/templates.js', 'js/app/**/*.js'])
      .pipe(concat('bundle.js'))
      .pipe(uglify())
      .pipe(gulp.dest('js/dist/'));
});

Run the ‘gulp’ task again to build, via the command line or via the VS Task Runner Explorer, or the post-build event (i haven’t yet learned to use ‘watch’ to auto-rebuild). Don’t forget to change the HTML back to load /bundle.js instead of the multiple JS files.

Running/reloading the page, we finally get the precompiled templates inserted into the html page, via the single bundle.js:

handlebars-test-html-bundle

This stuff gets a bit crazy! Why do this? I guess i want to compile, process, and optimize my javascript code.

The project code is here: https://github.com/nohea/Enehana.CodeSamples/tree/master/HandlebarsTest . Without the /node_modules directory, since the file paths are too long for Windows ZIP. To reconstitute the directory, cd to the project folder, and run:

cd HandlebarsTest\HandlebarsTest
npm update

That will reconstitute the packages from the internet, since all the dependencies are listed in the package.json file. It also allows you to easily exclude the node_modules directory from version control, and allow other developers to ‘npm update’ to populate their own directories.

Using Bower for JS package management instead of NPM

This is a follow up to my post: Learning Gulp with Visual Studio – the JavaScript Task Runner

In my last post, i did the following:

  • Created a web project
  • Installed Node.js
  • Installed Gulp for running JS build tasks
  • Installed more JS libraries using NPM (node package manager)
  • Created simple HTML+JS app w/jquery
  • Created gulp tasks to minify and bundle JS into main.js
  • run proof of concept
  • added gulp task to post-build event so it is run automatically

In this post, i will make some changes to the above, in that i will replace the JS package manager NPM with Bower.

Why? NPM works, but has some disadvantages vs. Bower. NPM packages all keep copies of their own dependencies. This can result in multiple versions of libraries, like JQuery, even different versions. Bower uses a ‘flat’ model, so only one version is installed at a time.

Well, what about just using NuGet? That is possible too, but NuGet is not good at updating dependent versions after initial installation. If you install different NuGet packages with the same dependency, the “last one wins”.

To be completly frank, i think it’s kind of crazy to have 2 different JS package managers in the same project. But Bower does solve the problem of having a single “flat” package dependencies. I found some hacks/workarounds to do it in NPM, but i just can’t see making the brain investment unless i do node all day every day.

Installing Bower

Open the Node Command Prompt.

We are going to install it using NPM, globally:

npm install -g bower

At that point, we can install libraries using bower, similar to how NPM works.

You also need to install msysgit , but we already installed it when installing Git Extensions.

Bower uses Git to install packages.

Configuring  / .bowerrc

Packages will install to the bower_components/ directory. If you want to change the defaults, create a .bowerrc directory and set it.

If you want to change that, create a file in your project named .bowerrc and enter the JSON to specify:

{
    "directory": "js/lib"
}

The packages will get installed there instead.

I found trouble creating the file with a leading dot in Windows Explorer or Visual Studio. However, using Notepad, you can save a file with a leading dot.

Installing Gulp to the project, as a development tool

First we create a package.json file for our project.

npm init

We are going to use the Gulp task build tool, but that is not a client-side library. It is used as a development build-time tool, so we are installing it using npm.

npm install gulp --save-dev

We also need to install the gulp-* plugins we need at build time:

npm install gulp-uglify --save-dev
npm install gulp-concat --save-dev

Those commands create entries in your package.json file, under the key devDependencies. That means they can be automatically installed when the project is built on another machine.

Installing client-side packages

The whole point of Bower is to use it for client-side packages like JQuery, Angular, etc.

First, in the node command prompt, we will initialize it by creating a bower.json file. You can do it manually, or do the init command, and fill out the questions.

Here is what i got:

{
  "name": "GulpBowerWebTest",
  "version": "0.0.1",
  "authors": [
    "raulg <raulg@xxxxx.yyy>"
  ],
  "description": "Test using Bower",
  "license": "Proprietary",
  "private": true,
  "ignore": [
    "**/.*",
    "node_modules",
    "bower_components",
    "js/lib",
    "test",
    "tests"
  ]
}

Now i’m going to install some libs, like jquery (specific version 1.9.x).

bower-install-jquery-commandprompt-2014-10-30

Note in Solution Explorer (w/”Show all Files” on) they installed to /js/lib/, as specified in our .bowerrc

bower-install-jquery-sol-expl-2014-10-30

Updating Gulpfile.js

I copied the static index.html and app.js files from my prior project. I’m using the same Gulpfile.js, with only some updates to the paths, since they are in different locations:

var gulp = require('gulp');
var uglify = require('gulp-uglify');
var concat = require('gulp-concat');

gulp.task('default', ['scripts'], function() {

});

gulp.task('scripts', function() {
    return gulp.src(['js/lib/jquery/jquery.js', 'scripts/**/*.js'])
      .pipe(concat('main.js'))
      .pipe(uglify())
      .pipe(gulp.dest('js/dist/'));
});

I’m trying out using Task Runner Explorer to run gulp. After tweaking and testing, i’m going to try checking the After Build event. This could be an alternative to setting it in the project’s post-build event. I’m not sure if its better yet, since i’ll need to have it work when building on the TeamCity CI server using MSBuild. Some VS tooling are not supported in MSBuild.

bower-taskrunner-afterbuildevent-2014-10-30

Now when i run the app, it works the same. The differences are that jQuery is at 1.9 version, and it should be easier to manage the client-side JS libs we use, and keep versions up to date and consistent (using the bower update command). I think that means jquery 1.9.x gets the latest, but will not go to 2.x if specified in the bower.json file.

References: