When to use Fetch in RequestEvent

[karchung0930]

I have go through many tutorials and it's not clear of when to use the fetch in the the RequestEvent object.

For example, in the +page.server.js:

export const actions = {
    default: async ({ request, fetch }) => {
        const requestContent = await fetch('/test');
        const responseContent = await requestContent.json();
    }
}

My question is in which file I can use the fetch from the RequestEvent:

1. +page.js
2. +page.server.js
3. +server.js

And when should I use it? One of the reason I could think of is when calling the local API such as /test instead of the absolute URl from outside the website. Am I correct? Any other circumstances?

[brunnerh]

See the note in the fetch APIs documentation:

A special version of fetch is available in load functions, server hooks and API routes for invoking endpoints directly during server-side rendering, without making an HTTP call, while preserving credentials. (To make credentialled fetches in server-side code outside load, you must explicitly pass cookie and/or authorization headers.) It also allows you to make relative requests, whereas server-side fetch normally requires a fully qualified URL.

So it's available pretty much everywhere and when the code runs on the server, it does not even involve a network call.

There is also some more documentation in the types section of the docs, see e.g. the LoadEvent. This documentation is also shipped with the types in the package, so it should be visible in IDEs if you inspect the fetch property of the event (if the event/function is typed correctly using TypeScript/JSDoc).