Lesson 18 / 28

async/await

Q: What happens to the rest of Node while one function awaits a Promise?

It keeps running other work. `await` only pauses the current async function — the event loop is free to handle other events meanwhile.

Write asynchronous code that reads like synchronous code.

await pauses, doesn't block

await pauses the surrounding async function until the Promise settles — the rest of Node keeps running.

import { readFile } from "node:fs/promises";

async function loadNotes() {
  const data = await readFile("notes.txt", "utf8");
  console.log(data.length, "characters");
}

loadNotes();

Parallel with Promise.all

Awaiting one call at a time is sequential — use Promise.all to run them together.

async function loadBoth() {
  const [notes, config] = await Promise.all([
    readFile("notes.txt", "utf8"),
    readFile("config.json", "utf8"),
  ]);
  console.log(notes.length, config.length);
}

Quick check: What happens to the rest of Node while one function awaits a Promise?

It freezes completely
It keeps running other work
It restarts the event loop

Answer

It keeps running other work — `await` only pauses the current async function — the event loop is free to handle other events meanwhile.