In JavaScript, async
and await
are keywords used in asynchronous programming to simplify working with promises. They are part of the ES2017 (ES8) specification and provide a more readable and sequential way to handle asynchronous operations.
Here's an explanation of async
and await
with code:
async
: Theasync
keyword is used to declare an asynchronous function. It allows the function to use theawait
keyword inside it and implicitly wraps the returned value in a resolved promise.Example : SDFSDF
async function fetchData() { // Asynchronous operation const response = await fetch('https://api.example.com/data'); const data = await response.json(); return data; }
In the above code, the
fetchData
function is declared asasync
. It performs an asynchronous operation by making an HTTP request to the specified URL using thefetch
API. Theawait
keyword is used to pause the execution of the function until the promise returned byfetch
resolves, allowing us to work with the response data.
Now let's talk about the next key function:
await
: The await
a keyword is used within an async
function to pause the execution of the function until a promise is resolved. It can only be used inside an async
function.
Example:
async function processData() {
try {
const result = await fetchData();
console.log(result);
} catch (error) {
console.error(error);
}
}
In this example, the
processData
function is declared asasync
. It calls thefetchData
function using theawait
keyword, which pauses the execution until the promise returned byfetchData
resolves. Once the promise resolves, the result is logged to the console. If an error occurs, it is caught and logged to the console as well.It's important to note that the use of
await
can only be done inside anasync
function. If you try to use it outside of anasync
function, it will result in a syntax error.
By using async
and await
, you can write asynchronous code in a more synchronous and readable manner, without the need for explicit promise chaining or callback functions.