Node.js event loop tutorial

This article mainly introduces the detailed explanation and examples of Node.js event loop. Node.js has multiple built-in events. We can bind and monitor events by introducing the events module and instantiating the EventEmitter class. Friends in need can refer to

Node.js event loop details and examples

• Node.js is a single-process single-thread application. But it supports concurrency through events and callbacks, so the performance is very high.

• Every API in Node.js is asynchronous and runs as a separate thread, uses asynchronous function calls, and handles concurrency.

• Node.js Basically all event mechanisms are implemented using the observer pattern in the design pattern.

• Node.js single thread is similar to entering a while(true) event loop until no event observer exits. Each asynchronous event generates an event observer. If an event occurs Just call the callback function.
  

Node.js has multiple built-in events. We can bind and listen to events by introducing the events module and instantiating the EventEmitter class. , the following example:

// 引入 events 模块 var events = require('events'); // 创建 eventEmitter 对象 var eventEmitter = new events.EventEmitter(); // 创建事件处理程序 var connectHandler = function connected() { console.log(1); // 触发 data_received 事件 eventEmitter.emit('data_received'); } // 绑定 connection 事件处理程序 eventEmitter.on('connection', connectHandler); // 使用匿名函数绑定 data_received 事件 eventEmitter.on('data_received', function(){ console.log(2); }); // 触发 connection 事件 eventEmitter.emit('connection'); console.log(3);

In a Node application, the function that performs an asynchronous operation takes the callback function as the last parameter, and the callback function receives the error object as the first parameter.

var fs = require("fs") fs.readFile('input.txt',function(err,data){ if(err) console.log(err) else console.log(data.toString()) }) console.log("程序执行完成")

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