You can also add handlers that mutate data, such as POST. In most cases, you should use form actions instead — you’ll end up writing less code, and it’ll work without JavaScript, making it more resilient.
Inside the keydown event handler of the ‘add a todo’ <input>, let’s post some data to the server:
<input
type="text"
autocomplete="off"
onkeydown={async (e) => {
if (e.key !== 'Enter') return;
const input = e.currentTarget;
const description = input.value;
const response = await fetch('/todo', {
method: 'POST',
body: JSON.stringify({ description }),
headers: {
'Content-Type': 'application/json'
}
});
input.value = '';
}}
/>Here, we’re posting some JSON to the /todo API route — using a userid from the user’s cookies — and receiving the id of the newly created todo in response.
Create the /todo route by adding a src/routes/todo/+server.js file with a POST handler that calls createTodo in src/lib/server/database.js:
import { json } from '@sveltejs/kit';
import * as database from '$lib/server/database.js';
export async function POST({ request, cookies }) {
const { description } = await request.json();
const userid = cookies.get('userid');
const { id } = await database.createTodo({ userid, description });
return json({ id }, { status: 201 });
}As with load functions and form actions, the request is a standard Request object; await request.json() returns the data that we posted from the event handler.
We’re returning a response with a 201 Created status and the id of the newly generated todo in our database. Back in the event handler, we can use this to update the page:
<input
type="text"
autocomplete="off"
onkeydown={async (e) => {
if (e.key !== 'Enter') return;
const input = e.currentTarget;
const description = input.value;
const response = await fetch('/todo', {
method: 'POST',
body: JSON.stringify({ description }),
headers: {
'Content-Type': 'application/json'
}
});
const { id } = await response.json();
data.todos = [...data.todos, {
id,
description
}];
input.value = '';
}}
/>You should only mutate
datain such a way that you’d get the same result by reloading the page.
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