//那new一个把
var test = new Promise(function(resolve, reject){resolve('数据');
});

function Async(){var test = new Promise(function(resolve,reject){resolve("成功返回数据")})return test;
}

Async()

Async().then(function(res){console.log(res)//....//可以对传过来的数据进行一系列操作
})

function Async1(){var p = new Promise(function(resolve, reject){resolve('随便什么数据1');});return p;
}
function Async2(){var p = new Promise(function(resolve, reject){resolve('随便什么数据2');});return p;
}
function Async3(){var p = new Promise(function(resolve, reject){resolve('随便什么数据3');});return p;
}Async1()
.then(function(data){console.log(data);return Async2();
})
.then(function(data){console.log(data);return Async3();
})
.then(function(data){console.log(data);
});

//接下来可以清楚的看到：// 随便什么数据1// 随便什么数据2// 随便什么数据3

function promise (fn) {if (typeof this !== 'object') { throw new TypeError('Promises must be constructed via new');}if (typeof fn !== 'function') {throw new TypeError('Promise constructor\'s argument is not a function');}this.state = "pending"; //定义状态this.msg="";var process=arguments[0];var that=this;process(function(){that.state="resolve"that.msg=arguments[0]},function(){that.state="reject"that.msg=arguments[0]})return this}promise.prototype.then=function(){constructor:promiseif(this.state == "resolve"){arguments[0](this.msg)}else if(this.status=='reject'&&arguments[1]){arguments[1](this.msg)}promise=new this.constructor(function (resolve,reject) {resolve("2")}) //每次调用then之后重新返回一个新的promise实例进行下一步then的调用//   console.log(this)//   console.log(promise)return promise}var mm =  new promise(function(resolve,reject){resolve("1")})mm.then(function(res){ //then回调
          console.log(res)}).then(function(res){console.log(res)})