实现一个简单的promise

1、最基本的功能：

function Promise(fn){    this.arr = [];    this.then = function(thParam){        thParam(this.arr);        //return this;    };    var that = this;    function resolve(parm){        that.arr.push(parm);        console.log(parm)    }    fn(resolve);}var p1 = new Promise(function(resolve){       resolve("参数给then");});p1.then(function(response){    console.log(response)});

2、链式调用
加上一个return this就可以了

function Promise(fn){    this.arr = [];    this.then = function(thParam){        thParam(this.arr);        return this;    };    var that = this;    function resolve(parm){        that.arr.push(parm);        console.log(parm)    }    fn(resolve);}var p1 = new Promise(function(resolve){       resolve("参数给then");});p1.then(function(response){    console.log(response)}).then(function(response){    console.log(response)});

参考资料：手写一个Promise