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This article mainly explains "what is js asynchrony". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is js asynchrony".

1. If the caller cannot get the expected result when the function returns, but needs to be obtained by some means in the future, then the function is asynchronous.

2. If the function is asynchronous, it returns immediately after the call, but does not immediately return the expected result.

The caller does not have to wait actively. When the caller gets the result, it will actively notify the caller through the callback function.

Example

/ / read the file fs.readFile ('hello.txt',' utf8', function (err, data) {console.log (data);}); / / Network request var xhr = new XMLHttpRequest (); xhr.onreadystatechange = xxx; / / add callback function xhr.open ('GET', url); xhr.send () / / initiator function Thank you for your reading. The above is the content of "what is js Asynchronous". After the study of this article, I believe you have a deeper understanding of what js async is, and the specific usage needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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