Use async/await to make asynchronous code easier to read and maintain. 1. You must use await in the async function, otherwise an error will be reported unless the environment supports top-level await; 2. Use try/catch to handle errors to avoid uncaught Promise rejections; 3. Try to perform independent asynchronous operations in parallel to avoid unnecessary serial waiting, and use Promise.all to improve performance. When using async/await correctly, you need to pay attention to always handling Promise results, reasonably managing errors, and optimizing execution order, so that you can write asynchronous code efficiently.
You work with async/await in JavaScript by writing asynchronous code that looks and behaves more like synchronous code, making it easier to read and maintain. Here's how it works and how to use it effectively.
What is async/await ?
async/await is built on top of Promises and provides a cleaner syntax for handling asynchronous operations. An async function always returns a Promise, and await can only be used inside an async function to pause execution until the Promise settlements.
async function fetchData() {
const response = await fetch('https://api.example.com/data');
const data = await response.json();
return data;
} This is much cleaner than chaining .then() calls.
How to Use async/await Properly
1. Always use await inside async functions
You can't use await at the top level of your script unless you're in a module with top-level await (available in modern environments).
// ? Works
async function getUser() {
const res = await fetch('/user');
return await res.json();
}
// ? Throws error (unless in module with top-level await)
// const data = await fetch('/user').then(r => r.json()); If you're not in an async function, you'll need to fall back to .then() or wrap the code in an async IIFE:
(async () => {
const data = await fetchData();
console.log(data);
})(); 2. Handle errors with try/catch
Since await can cause the code to throw if the Promise is rejected, wrap it in a try/catch block.
async function safeFetch() {
try {
const response = await fetch('https://api.example.com/data');
if (!response.ok) throw new Error('Network error');
const data = await response.json();
console.log(data);
} catch (error) {
console.error('Fetch failed:', error.message);
}
} This is cleaner than using .catch() on Promises.
3. Run async operations in parallel when possible
Using await one after another blocks execution. If you need multiple independent async operations, start them all first, then await their results.
async function fetchMultiple() {
// ? Slower: one after another
// const a = await fetch('/a');
// const b = await fetch('/b');
// ? Faster: run in parallel
const promiseA = fetch('/a');
const promiseB = fetch('/b');
const resA = await promiseA;
const resB = await promiseB;
return [await resA.json(), await resB.json()];
} Or use Promise.all() for even cleaner syntax:
const [dataA, dataB] = await Promise.all([ fetch('/a').then(res => res.json()), fetch('/b').then(res => res.json()) ]);
Common Pitfalls to Avoid
- Forgetting
await: If you forgetawait, you get a Promise instead of the resolved value. - Top-level
awaitsupport : Not available in all environments (eg, older Node.js or non-module scripts). - Overusing
awaitserially : Can slow down your app unnecessarily. - Not handling errors : Uncaught rejections can crash your app.
Basically, async/await makes async code easier to write and debug — just remember it's just syntactic sugar over Promises. Use try/catch , avoid unnecessary blocking, and handle edge cases. That's how you work with it well.
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