use-server-directive

Universal use server functions

Install

npm i use-server-directive

yarn add use-server-directive

pnpm add use-server-directive

Features

Server functions

Like the original "use server" directive, the compiler supports functions.

async function doStuff(x, y) {
  "use server";
  await foo(x);
  await bar(y);
}
// also works for arrow functions

const doStuff = async (x, y) => {
  "use server";
  await foo(x);
  await bar(y);
};

The compiler also supports async generators

async function* doStuff(x, y) {
  "use server";
  yield foo(x);
  yield bar(y);
}

NOTE Server functions are only valid for async functions.

Server blocks

The original "use server" is limited to functions, but what if you could mark block statements with the same directives?

if (someCond()) {
  'use stuff';
  await doStuff();
}

use-server-directive supports server blocks in almost all statements that supports it:

• if-else
• try-catch-finally
• for
• for-in
• for-of
• for await
• while
• do-while
• labeled statements

Server blocks also supports break, continue, return and throw statements, as well as yield expressions and delegations.

for (const item of items) {
  'use server';
  await processItem(item);
}

NOTE Server blocks are only supported within async functions and at top-level scope (since modules now support top-level await)

Closure extraction

use-server-directive supports closure extraction

async function foo() {
  const prefix = 'Message: ';

  async function postMessage(message) {
    'use server';
    await addMessage(prefix + message);
  }
}

Streaming server functions

If a server function returns a value with a Promise, ReadableStream or AsyncIterable, those instances' values are going to be streamed through the response.

async function getMessage() {
  'use server';
  return {
    // `getAsyncData` returns a Promise
    // On the client-side, this object is going to
    // be received immedatiely, but the value
    // to which the Promise resolves into
    // is going to be streamed after.
    message: getAsyncData(),
  };
}

Advanced serialization

use-server-directive supports a wide range of data types, you can check the compatibility table here

Customizable directive

Integrations

• Vite

Examples

• Astro
• SvelteKit

Preloading

There are instances where a server function is only imported through a dynamic import, which causes unspecified registration timing, wherein the function might be available on the client but not on the server.

To allow registration of server functions immediately, you can import use-server-directive/preload on any server entrypoints that will load immediately when the server runs.

import 'use-server-directive/preload';

Sponsors

License

MIT © lxsmnsyc