SvelteKit allows you to create more than just pages. We can also create API routes by adding a +server.js file that exports functions corresponding to HTTP methods: GET, PUT, POST, PATCH and DELETE.

This app fetches data from a /roll API route when you click the button. Create that route by adding a src/routes/roll/+server.js file:

export function GET() {
	const number = Math.floor(Math.random() * 6) + 1;

	return new Response(number, {
		headers: {
			'Content-Type': 'application/json'
		}
	});
}

Clicking the button now works.

Request handlers must return a Response object. Since it’s common to return JSON from an API route, SvelteKit provides a convenience function for generating these responses:

import { json } from '@sveltejs/kit';

export function GET() {
	const number = Math.floor(Math.random() * 6) + 1;

	return new Response(number, {
		headers: {
			'Content-Type': 'application/json'
		}
	});
	return json(number);
}