Lesson04

回调函数与事件

一、函数

1.异步式readFile

var fs = require('fs');
fs.readFile("file.txt","UTF-8",function(err,data){
    if(err){
          console.log(err);
    }
    else{
         console.log(data);
    }
});
console.log("end");

2.同步式readFileSync

var fs = require('fs');
var data = fs.readFileSync("file.txt","UTF-8");
console.log(data);
console.log("end");

readFile参考网页

二、事件

1.声明事件对象

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

2.注册事件

event.on("some_event",function(number1,number2){
    console.log("这是一个自定义事件");
    console.log("number1 = " + number1);
    console.log("number2 =" + number2);
});

3.触发事件

setTimeout(function(){
    event.emit("some_event",10000,500);//number1=10000,number2=500
})

Event参考网页