Node.js event

chapter

• Node.js Introduction
• Node.js entry
• Node.js modules
• Node.js HTTP module
• Node.js file system module
• Node.js URL module
• Node.js NPM
• Node.js event
• Node.js upload files
• Node.js Send Email

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Node.js is ideal for event-driven applications.

Node.js events

Every movement on the computer is an event, such as: open the file, visit the website.

Node.js The object can trigger events, such as readStream object when opening and closing the file will trigger events:

Examples

var fs = require('fs');
var rs = fs.createReadStream('./demofile.txt');
rs.on('open', function () {
  console.log('The file is open');
});

Event module

Node.js has a built-in module Events, can be used to create the trigger and listen for events.

Using the require()method introduced Events module.

var events = require('events');

EventEmitter objects

EventEmitterThe main object is the object handling the event. For example, you can use EventEmitteran object, assign an event handler for the event.

In the following example, we created a function, it will perform in the "scream" event is triggered.

To trigger the event, use the emit()method.

Examples

var events = require('events');
var eventEmitter = new events.EventEmitter();

//创建一个事件处理程序:
var myEventHandler = function () {
  console.log('I hear a scream!');
}

//将事件处理程序分配给事件:
eventEmitter.on('scream', myEventHandler);

//触发“scream”事件:
eventEmitter.emit('scream');