async and await are powerful features in JavaScript that make working with Promises easier and more readable. They allow you to write asynchronous code that looks and behaves like synchronous code. Here's a quick overview:
async Function
- Definition: An async function is a function that returns a Promise. It allows you to use await within it.
- Syntax:
async function myFunction() {
// Your code here
}
await Keyword
- Definition: The await keyword can only be used inside an async function. It pauses the execution of the async function and waits for the Promise to resolve or reject.
- Syntax:
let result = await somePromise;
Example
Here's a simple example to demonstrate how async and await work together:
function fetchData() {
return new Promise((resolve) => {
setTimeout(() => {
resolve('Data fetched');
}, 2000);
});
}
async function getData() {
console.log('Fetching data...');
const data = await fetchData();
console.log(data);
}
getData();
In this example:
- fetchData is a function that returns a Promise, which resolves after 2 seconds.
- getData is an async function that uses await to wait for fetchData to resolve.
- When getData is called, it logs "Fetching data...", waits for fetchData to resolve, and then logs "Data fetched".
Benefits
- Readability: async/await makes asynchronous code look more like synchronous code, which can be easier to read and understand.
- Error Handling: You can use try...catch blocks with async/await to handle errors more cleanly.
Error Handling Example
async function getData() {
try {
console.log('Fetching data...');
const data = await fetchData();
console.log(data);
} catch (error) {
console.error('Error fetching data:', error);
}
}
getData();
In this example, if fetchData were to reject, the error would be caught by the catch block, and "Error fetching data:" would be logged along with the error message.
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