Inertia.js Svelte Adapter

Installation

Install using NPM:

npm install @inertiajs/inertia @inertiajs/inertia-svelte --save

Configure server-side framework

The first step when using Inertia.js is to configure your server-side framework. This primarily includes setting up a root template and updating your endpoints to return a proper Inertia response. For an example of this, see our Laravel adapter.

Setting up Webpack

You'll need to setup the svelte-loader for webpack. You can do it manually following these instructions, or just using laravel-mix-svelte.

Here is an example Webpack configuration that uses Laravel Mix. Note the @ alias to the /resources/js directory.

const mix = require('laravel-mix')
const path = require('path')

mix
  .js('resources/js/app.js', 'public/js')
  .sass('resources/sass/app.scss', 'public/css')
  .webpackConfig({
    output: { chunkFilename: 'js/[name].js?id=[chunkhash]' },
    resolve: {
      mainFields: ['svelte', 'browser', 'module', 'main'],
      alias: {
        '@': path.resolve('resources/js'),
      },
    },
    module: {
      rules: [
        {
          test: /\.(svelte)$/,
          use: {
            loader: 'svelte-loader',
            options: {
              emitCss: true,
              hotReload: true,
            },
          },
        },
      ],
    },
  })

Setup dynamic imports

We recommend using code splitting with Inertia.js. To do this we need to enable dynamic imports. We'll use a Babel plugin to make this work. First, install the plugin:

npm install @babel/plugin-syntax-dynamic-import --save

Next, create a .babelrc file in your project with the following:

{
  "plugins": ["@babel/plugin-syntax-dynamic-import"]
}

Alternatively, if you're using Laravel Mix, you can put this in your webpack.mix.js file:

mix.babelConfig({
  plugins: ['@babel/plugin-syntax-dynamic-import'],
})

Initializing Svelte

Next, update your main JavaScript file to boot your Inertia app. All we're doing here is initializing Svelte with the base Inertia page component.

import { InertiaApp } from '@inertiajs/inertia-svelte'

const app = document.getElementById('app')

new InertiaApp({
  target: app,
  props: {
    initialPage: JSON.parse(app.dataset.page),
    resolveComponent: name => import(`@/Pages/${name}.svelte`).then(module => module.default),
  },
})

The resolveComponent is a callback that tells Inertia how to load a page component. It receives a page name (string), and must return a component instance.

Using Inertia without code splitting

It's possible to also use Inertia without code splitting. This will generate one larger JavaScript bundle, instead of many smaller ones. With this approach, the dynamic imports Babel plugin is not required.

One way to do this is manually loading all your page components:

import { InertiaApp } from '@inertiajs/inertia-svelte'

const app = document.getElementById('app')

const pages = {
  'Dashboard/Index': require('./Pages/Dashboard/Index.svelte').default,
  'Users/Index': require('./Pages/Users/Index.svelte').default,
  'Users/Create': require('./Pages/Users/Create.svelte').default,
  // etc...
}

new InertiaApp({
  target: app,
  props: {
    initialPage: JSON.parse(app.dataset.page),
    resolveComponent: name => pages[name],
  },
})

Another option is to use required.context to automatically register all your page components.

import { InertiaApp } from '@inertiajs/inertia-svelte'

const app = document.getElementById('app')

const files = require.context('./', true, /\.svelte$/i)

new InertiaApp({
  target: app,
  props: {
    initialPage: JSON.parse(app.dataset.page),
    resolveComponent: name => files(`./Pages/${name}.svelte`).default,
  },
})

Creating a base layout

While not required, for most projects it makes sense to create a default site layout that your specific pages can extend. Save this to /Shared/Layout.svelte.

<script>
  import { InertiaLink } from '@inertiajs/inertia-svelte'

  export let title
</script>

<svelte:head>
    <title>{title}</title>
</svelte:head>

<main>
  <header>
    <InertiaLink href="/">Home</InertiaLink>
    <InertiaLink href="/about">About</InertiaLink>
    <InertiaLink href="/contact">Contact</InertiaLink>
  </header>

  <article>
    <slot />
  </article>
</main>

Creating page components

With Inertia.js, each page in your application is a JavaScript component. Here's an example of a page component. Save this to /Pages/Welcome.svelte. Note how it extends the Layout.svelte component we created above.

<script>
  import Layout from '@/Shared/Layout.svelte';
</script>

<Layout title="Welcome">
  <h1>Welcome</h1>
  <p>Welcome to my first Inertia.js app!</p>
</Layout>

Creating links

To create an Inertia link, use the <InertiaLink> component.

<script>
  import { InertiaLink } from '@inertiajs/inertia-svelte'
</script>

<InertiaLink href="/">Home</InertiaLink>

You can also specify the browser history and scroll behaviour. By default all link clicks "push" a new history state, and reset the scroll position back to the top of the page. However, you can override these defaults using the replace and preserveScroll attributes.

<InertiaLink href="/" preserveScroll replace>Home</InertiaLink>

You can also specify the method for the request. The default is GET, but you can also use POST, PUT, PATCH, and DELETE.

<InertiaLink href="/logout" method="post">Logout</InertiaLink>

You can add data using the data attribute:

<InertiaLink href="/endpoint" method="post" data={{ foo: bar}}>Save</InertiaLink>

You can also preserve a page component's local state using the preserveState attribute. This will prevent a page component from fully re-rendering. This is especially helpful with forms, since you can avoid manually repopulating input fields, and can also maintain a focused input.

<input value={query} on:change={handleChange} />
<InertiaLink href="/search" data={query} preserveState>Search</InertiaLink>

Manually making visits

In addition to clicking links, it's also very common to manually make Inertia visits. The following methods are available. Take note of the defaults.

// Make a visit
Inertia.visit(url, { method: 'get', data: {}, replace: false, preserveState: false, preserveScroll: false })

// Make a "replace" visit
Inertia.replace(url, { method: 'get', data: {}, preserveState: true, preserveScroll: false })

// Make a "reload" visit to the current url
Inertia.reload({ method: 'get', data: {}, preserveState: false, preserveScroll: false })

// Make a POST visit
Inertia.post(url, data, { replace: false, preserveState: true, preserveScroll: false })

// Make a PUT visit
Inertia.put(url, data, { replace: false, preserveState: true, preserveScroll: false })

// Make a PATCH visit
Inertia.patch(url, data, { replace: false, preserveState: true, preserveScroll: false })

// Make a DELETE visit
Inertia.delete(url, { replace: false, preserveState: false, preserveScroll: false })

Just like with an <InertiaLink>, you can control the history control behaviour using replace, scroll behaviour using preserveScroll, and local component state behaviour using preserveState.

Accessing page data in other components

Sometimes it's necessary to access the page data (props) from a non-page component. One really common use-case for this is the site layout. For example, maybe you want to show the currently authenticated user in your site header. This is possible using Svelte's store feature.

The easiest way to access page props is with our page store.

<script>
  import { InertiaLink, page } from '@inertiajs/inertia-svelte'
</script>

<main>
  <header>
    You are logged in as: {$page.auth.user.name}

    <nav>
      <InertiaLink href="/">Home</InertiaLink>
      <InertiaLink href="/about">About</InertiaLink>
      <InertiaLink href="/contact">Contact</InertiaLink>
    </nav>
  </header>

  <article>
    <slot />
  </article>
</main>

Remembering local component state

When navigating browser history, Inertia reloads pages using prop data cached in history state. Inertia does not, however, cache local component state, since this is beyond its reach. This can lead to outdated pages in your browser history. For example, if a user partially completes a form, then navigates away, and then returns back, the form will be reset and their work will have been lost.

To mitigate this issue, you can use the remember store to tell Inertia.js which local component state to cache.

<script>
  import { Inertia } from '@inertiajs/inertia'
  import { remember } from '@inertiajs/inertia-svelte'

  let form = remember({
    first_name: null,
    last_name: null,
  })
</script>

<form on:submit|preventDefault={() => Inertia.post('/contact', $form)}>
  <label for="first_name">First Name:</label>
  <input id="first_name" bind:value={$form.first_name}></div>

  <label for="last_name">Last name:</label>
  <input id="last_name" bind:value={$form.last_name}></div>

  <button type="submit">Save</button>
</form>

remember returns a store. Prefix the variable you assign it to with $ to take advantage of auto-subscription.

If your page contains multiple components using the remember functionality, you'll need to provide a unique key for each component. For example, Users/Create. If you have multiple instances of the same component on the page, be sure to include a unique identifier for each of those instances. For example, Users/Edit:{id}.

<script>
  import { Inertia } from '@inertiajs/inertia'
  import { page, remember } from '@inertiajs/inertia-svelte'

  $: ({ user } = $page)

  let form = remember({
    first_name: null,
    last_name: null,
  }, `Users/Edit:${user.id}`)

  // ...
</script>

hspin/inertia-svelte