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The main content of this article is to explain "what is the meaning of nodejs callback hell", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Next, let the editor take you to learn "what is the meaning of nodejs callback hell?"

In nodejs, basically, the operation results of "Ibank O" need to be handled in the callback function. When dealing with multiple events, the callback function will be nested layer by layer, which is the callback hell; that is, an asynchronous request is nested with an asynchronous request, and an asynchronous request depends on the execution result of another, and the callback is used to nest each other.

This article operating environment: Windows10 system, nodejs version 12.19.0, Dell G3 computer.

What is the hell of nodejs callback?

Basically, the results of the operation of nodejs need to be handled in the callback function. When dealing with multiple events, the callback function will be nested layer by layer, which is called callback hell.

An asynchronous request is nested with an asynchronous request, and one asynchronous request depends on the execution result of the other, nesting each other by callback

The biggest highlight of Nodejs lies in the event-driven, non-blocking Imax O model, which makes Nodejs has a strong concurrent processing ability, which is very suitable for writing network applications. In Nodejs, most of the iUnip O operations are almost asynchronous, that is, the results of our operations need to be handled in the callback function, such as the following function that reads the contents of the file:

Fs.readFile ('/ etc/passwd', function (err, data) {if (err) throw err; console.log (data);})

So, what if we read two files and merge the contents of the two files together? Most people who have not been exposed to js will probably do this:

Fs.readFile ('/ etc/passwd', function (err, data) {if (err) throw err; fs.readFile ('/ etc/passwd2', function (err, data2) {if (err) throw err; / / processes data and data2 data} here);})

If you deal with multiple similar scenarios, isn't it a layer-by-layer nesting of callback functions? this is the so-called callback pyramid or callback hell.

At this point, I believe you have a deeper understanding of "what is the meaning of nodejs callback hell". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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