Hooks / handle • Svelte Tutorial

Advanced SvelteKit Hooks handle

SvelteKit provides several hooks — ways to intercept and override the framework’s default behaviour.

The most elementary hook is handle, which lives in src/hooks.server.js. It receives an event object along with a resolve function, and returns a Response.

resolve is where the magic happens: SvelteKit matches the incoming request URL to a route of your app, imports the relevant code (+page.server.js and +page.svelte files and so on), loads the data needed by the route, and generates the response.

The default handle hook looks like this:

src/hooks.server

export async function handle({ event, resolve }) {
	return await resolve(event);
}

For pages (as opposed to API routes), you can modify the generated HTML with transformPageChunk:

src/hooks.server

export async function handle({ event, resolve }) {
	return await resolve(event, {
		transformPageChunk: ({ html }) => html.replace(
			'<body',
			'<body style="color: hotpink"'
		)
	});
}

You can also create entirely new routes:

src/hooks.server

export async function handle({ event, resolve }) {
	if (event.url.pathname === '/ping') {
		return new Response('pong');
	}

	return await resolve(event, {
		transformPageChunk: ({ html }) => html.replace(
			'<body',
			'<body style="color: hotpink"'
		)
	});
}

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Redirects The RequestEvent object

<h1>hello world</h1>

<a href="/ping">ping</a>

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