原生js写简单的promise 及使用

function MyPromise(func) {

var self =this;

    var count =0;

    this.cbklist = [];

    this.then =function(callback) {

this.cbklist.push(callback);

        return this;

    }

this.success =function() {

if (count == self.cbklist.length)return;

        self.cbklist[count++](self.success);

    }

setTimeout(function() {

func(self.success);

    }, 0);

}

function ajaxA(success){

setTimeout(function(){

console.log("AAAAAAAAAA");

        success();

    }, 3000);

}

function ajaxB(success){

setTimeout(function(){

console.log("BBBBBBBBBB");

        success();

    }, 2000);

}

function ajaxC(success){

setTimeout(function(){

console.log("CCCCCCCCCC");

        success();

    }, 1000);

}

function ajaxD(){

setTimeout(function(){

console.log("DDDDDDDDD");

    }, 2000);

}

new MyPromise(ajaxA).then(ajaxB).then(ajaxC).then(ajaxD);

来源https://www.cnblogs.com/liuliang-wifi/p/6832850.html