node.js接收异步任务结果的两种方法----callback和事件广播

• 事件广播 发送方调用emit方法，接收方调用on方法，无论发送方或是接收方，都会工作在一个频道

声明了一个模块，用于读取mime.json中的记录
var fs = require('fs');
var events = require('events');
var eventemitter = new events.EventEmitter();
var getmimetype = function (path,eventemitter,suffix) {
    fs.readFile(path,function (err,data) {
        if(err){
            console.log(err);
            return false;
        }
        var filedata = JSON.parse(data.toString());
        eventemitter.emit('wenwa',filedata[suffix]);
        //console.log(filedata[suffix])
    })
};
module.exports = getmimetype;

• 接收方

也就是在另一个文件中调用写好的模块，并声明广播的接收方
var eventer = require('./readfile_events');
var fs = require('fs');
var events = require('events');
var eventemitter = new events.EventEmitter();
eventer('./mime.json',eventemitter,'.css');
eventemitter.on('wenwa',function (data) {
    console.log(data)
});

• 回调函数

//定义模块
var fs = require('fs');
var gettype = function (suffix,callback) {
    fs.readFile('./mime.json',function (err,data) {
        if(err){
            console.log(err);
            return false;
        }
        var filedata = JSON.parse(data.toString());
        //console.log(filedata[suffix]);
        callback(filedata[suffix])
    })
};
module.exports = gettype;

//调用模块
var gettype = require('./readfilecallback.js');
var fs = require('fs');
var events = require('events');
var eventemitter = new events.EventEmitter();
gettype('.323',mycallback);
function mycallback(data) {
    console.log(data)
}

标签：node,fs,require,eventemitter,js,callback,var,data,events
来源： https://www.cnblogs.com/saintdingspage/p/11737419.html