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This article mainly introduces the relevant knowledge of how to use the JavaScript asynchronous function, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this article on how to use the JavaScript asynchronous function. Let's take a look at it.

Asynchronous function

Asynchronous function (async function) is the specification of the ECMAScript 2017 (ECMA-262) standard and is supported by almost all browsers except Internet Explorer.

We wrote a Promise function in Promise:

Case study

Function print (delay, message) {

Return new Promise (function (resolve, reject) {

SetTimeout (function () {

Console.log (message)

Resolve ()

}, delay)

})

}

Then output three lines of text at different intervals:

Case study

Print (1000, "First") .then (function () {

Return print (4000, "Second")

}) .then (function () {

Print (3000, "Third")

})

We can make this code look better:

Case study

Async function asyncFunc () {

Await print (1000, "First")

Await print (4000, "Second")

Await print (3000, "Third")

}

AsyncFunc ()

Ha! Doesn't this make asynchronous operations as easy as synchronous operations!

The answer this time is yes. The await instruction can be used in the asynchronous function async function, and the await instruction must be followed by a Promise. The asynchronous function will be paused in the Promise run until it is finished.

Asynchronous functions actually work in exactly the same way as Promise's native API, except that they are easier for programmers to read.

The mechanism for handling exceptions will be implemented with try-catch blocks:

Case study

Async function asyncFunc () {

Try {

Await new Promise (function (resolve, reject) {

Throw "Some error"; / or reject ("Some error")

})

} catch (err) {

Console.log (err)

/ / Some error will be output

}

}

AsyncFunc ()

If Promise has a normal return value, the await statement also returns it:

Case study

Async function asyncFunc () {

Let value = await new Promise (

Function (resolve, reject) {

Resolve ("Return value")

}

)

Console.log (value)

}

AsyncFunc ()

The program outputs:

Return value

This is the end of the article on "how to use JavaScript Asynchronous functions". Thank you for reading! I believe you all have a certain understanding of the knowledge of "how to use JavaScript asynchronous functions". If you want to learn more, you are welcome to follow the industry information channel.

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