Node.js is a platform built on the Chrome JavaScript runtime.
Node.js is an event-driven I/O server-side JavaScript environment based on Google's V8 engine. The V8 engine executes Javascript very quickly and has very good performance.
Node.js EventEmitter syntax
Node.js All asynchronous I/O operations will send an event to the event queue when completed.
Many objects in Node.js will emit events: a net.Server object will emit an event every time there is a new connection, and a fs.readStream object will emit an event when the file is opened. All of these event-generating objects are instances of events.EventEmitter.
Node.js EventEmitter example
//event.js file
var EventEmitter = require('events').EventEmitter;
var event = new EventEmitter();
event.on('some_event', function() { console.log('some_event 事件触发'); });
setTimeout(function() { event.emit('some_event'); }, 1000);