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This article mainly explains "how to achieve asynchronous processing in Node.js". 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 "how to achieve asynchronous processing in Node.js".

Various writing methods of asynchronism

Task description: there are three files Jay.txt, Angela.txt and Henry.txt in the root directory of the project. Read the contents of these three files and print them in turn.

Let's use various asynchronous processing methods to accomplish this task.

Callback function

Ps: let's take a look at how Nodejs handles async (getting asynchronous data and processing it).

Method 1. Callback function mode

Encapsulate an asynchronous method such as readFile into a custom function by passing the result of the asynchronous method to the callback function parameter of the custom method. The details are as follows (take the readFile method of fs module as an example):

/ / Encapsulation var func = function (filePath,callback) {fs.readFile (filePath, function (err, data) {if (err) {return false;} callback (data);})} / / call func ('. / a.txtreply, function (res) {/ / process the data returned by the asynchronous method console.log (res);})

Method 2. Event-driven mode

Use the node events module to transmit the results returned by the asynchronous method using its EventEmitter object to broadcast and receive broadcasts. The details are as follows (still take the readFile asynchronous method of the fs module as an example):

Var events = require ('events'); var EventEmitter = new events.EventEmitter (); fs.readFile ('. / a.txtbroadcast, function (err, data) {/ / broadcast that sends out readData signals after data reading, and sends data data out of EventEmitter.emit ('readData', data) }) / / listen to the readData signal and process the monitored data (you can also define the monitoring first, and then do the asynchronous read operation) EventEmitter.on ('readData', function (res) {/ / process the data console.log (res) obtained by asynchronous reading) }) Thank you for your reading. The above is the content of "how to achieve asynchronous processing in Node.js". After the study of this article, I believe you have a deeper understanding of how to achieve asynchronous processing in Node.js, and the specific use 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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