Async/Await

This lesson covers Async/Await. You do not need to memorize everything. Understand the flow first.

What you will learn

• What async/await means — in normal words, not textbook words
• How it works step by step
• Code you can run today on your laptop
• Where teams use this in real projects

Before you start

• Software: Node.js LTS from nodejs.org, VS Code, and a terminal
• Knowledge: Earlier lessons in this Node.js course
• Previous lesson: Promises — Complete Guide

Explain it simply

async/await is syntax on top of Promises. You write async code that looks synchronous but still does not block the server.

Why developers use this

• Easiest to read and maintain
• try/catch for errors
• Standard in modern Node and Express handlers

How it works (step by step)

1. Your code starts a task (read file, query DB, timer).
2. Node continues other work instead of waiting idle.
3. When the task finishes, your callback, Promise, or await runs.
4. Errors go in catch or .catch() — never ignore them.

Code example — type this yourself

const fs = require('fs/promises');

async function loadConfig() {
  try {
    const raw = await fs.readFile('config.json', 'utf8');
    return JSON.parse(raw);
  } catch (err) {
    console.error('Config missing, using defaults');
    return { port: 3000 };
  }
}

await pauses only inside the async function — other requests can still run.

What each part does

• const fs = require('fs/promises'); — Loads a built-in module or package you installed with npm.
• async function loadConfig() { — Async work — Node can serve other users while this waits.
• try { — Catches errors so one failure does not crash the whole server.
• const raw = await fs.readFile('config.json', 'utf8'); — Async work — Node can serve other users while this waits.
• return JSON.parse(raw); — Line 5: runs as written.
• } catch (err) { — Catches errors so one failure does not crash the whole server.
• console.error('Config missing, using defaults'); — Line 7: runs as written.
• return { port: 3000 }; — Line 8: runs as written.

Real life: where Async/Await shows up

An online store uses Async/Await so hundreds of users can check order status at once. While one request waits for the database, Node handles other users instead of freezing. Start small: one feature working beats a perfect architecture on paper.

Try it yourself — hands-on

1. Create config.json with {"port":4000}
2. Call loadConfig() from an async main()
3. Delete config.json and see the fallback

Common mistakes (avoid these)

• Using await without async — syntax error.

Interview note

Interviewers often ask: “What is Async/Await?” Answer in one sentence, then give a tiny example you actually ran.

Summary

• async functions return Promises
• await waits for a Promise
• Use try/catch for errors