Summary - async/await

Combine async/await and Promise.all to write a file processor.

Summary - async/await

In this group you learned the async/await syntax. async functions always return a Promise; await lets you wait for a Promise's result in a synchronous-looking way. You catch errors with try/catch.

For parallel work you use await Promise.all([...]); for sequential dependent work you write consecutive await calls. Choosing the right approach shapes both readability and speed. async/await offers a flatter flow than then chains.

Exercise Your turn: get a value with await

Define async function run(). Write const v = await Promise.resolve("done"). Log it with console.log(v). Call run().

Show example solution

async function run() {
  const v = await Promise.resolve("done");
  console.log(v);
}
run();

Exercise Your turn: try/catch with await

Define async function run(). Inside a try block, write const v = await Promise.reject(new Error("error")). Inside catch (err), write console.log(err.message). Call run().

Show example solution

async function run() {
  try {
    const v = await Promise.reject(new Error("error"));
  } catch (err) {
    console.log(err.message);
  }
}
run();

Test yourself

async/await parts

async

returns a Promise
await

waits for result
try/catch

catches errors
What does a returned value become in an async function?
- It throws an error
- It is returned as is
- It becomes undefined
- It is wrapped in a Promise
Show answer

It is wrapped in a Promise — An async function's return value is wrapped in a Promise.

Next lesson: fs.promises

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