function promise(option){
const that = this; //防止this指针的改变
that.status = 'pending'; //初始化的状态值
that.value = null; //保存外部传入的值
//创建执行resolve时的函数
function reslove(value){
if(that.status=='pending'){
that.status = 'resolve'; //改变status的状态
that.value = value;
}
// console.log(that)
}
//创建执行reject的函数也就是失败函数
function reject(value){
if(that.status == 'pending'){
that.status = 'reject'; ;//改变status的状态
that.value = value
}
}
//可能声明了promise还在等待状态，对齐进行处理
try{
option(reslove,reject)
}catch(e){
reject(e)
}
// option(reslove,reject)
}
//创建链式调用
promise.prototype.then = function(fn1,fn2){
if( this.status == 'resolve'){
fn1(this.value)
}else{
fn2(this.value)
}
}
let pro = new promise(function(res,rej){
res('123')
})
// pro.then((data)=>{
// console.log(data);
// })
pro.then(function(data){
console.log(data);
},function(err){
console.log(err);
})
