未写完，写完了讲解一下
/*
value:Promise值
status:Promise状态 pending等待 resolved完成 rejected报错
*/
class NewPromise {
constructor(fun) {
this.value = null;
this.status = 'pending';
this.error=null
this.onFulfilled = [];//完成时数组
this.onRejected = [];//未完成的数组
const resolve = (value)=> {
if(this.status==='pending'){
this.value=value;
this.status='resolved'
this.onFulfilled.forEach(callback=>callback(this.value))
this.onFulfilled=[]
}
};
const reject = (error)=> {
if(this.status==='pending'){
this.error=error;
this.status='rejected'
this.onRejected.forEach(callback=>callback(this.error))
this.onRejected=[]
throw error
}
};
try{
fun(resolve,reject)
}catch(e){
reject(e)
}
}
then(resolveCall,rejectCall){
let bindPromise;
let self = this;
if(this.status==='pending'){
// this.onFulfilled.push(resolve)
return bindPromise = new NewPromise((resolve, reject) => {
self.onFulfilled.push((value) => {
try {
let x = resolveCall(value);
resolve(x);
} catch (e) {
reject(e);
}
});
// self.onRejected.push((error) => {
// try {
// let x = rejectCall(error);
// resolve(x);
// } catch (e) {
// reject(e);
// }
// });
});
}
else if(this.status==='resolved'){
// resolveCall(this.value)
return bindPromise = new NewPromise((resolve, reject) => {
let x = resolveCall(this.value);
resolve(x)
});
}
else{
rejectCall(this.error)
}
}
// static resolve(val) {//静态方法
// this.status = "resolved";
// this.value = val;
// return this
// }
}
const newPromise=new NewPromise((resolve)=>{
console.log(1)
setTimeout(()=>{
console.log(4)
resolve(111)
},1000)
console.log(2)
})
.then(res=>{
console.log(res)
// return 100
})
// .then(res=>{
// console.log(res)
// })
console.log(newPromise)
