promise简易版
class Promises {
constructor(cb) {
this.thenArr = []; //存放then函数里面的成功的函数和失败的函数
this.cb = cb; //promise中的回调函数
this.count = 0; //计数
this.returnText = null;//返回值
this.resolve = this.resolve.bind(this);
this.reject = this.reject.bind(this);
this.cb(this.resolve, this.reject);
}
static all(promiseData) {
let resultData = [];
let errData = [];
return new Promises((res, rej) => {
promiseData.forEach(i => {
i.then(data => {
resultData.push(data);
test();
}, (err) => {
errData.push(err);
testerr();
})
})
function test() {
if (promiseData.length === resultData.length) {
res(resultData)
}
}
function testerr() {
if (errData.length > 0) {
rej(errData[0])
}
}
})
}
static race(promiseData) {
let resultData = [];
let errData = [];
return new Promises((res, rej) => {
promiseData.forEach(i => {
i.then(data => {
resultData.push(data);
test();
}, (err) => {
errData.push(err);
testerr();
})
})
function test() {
if (promiseData.length > resultData.length) {
res(resultData)
}
}
function testerr() {
if (errData.length === errData.length) {
rej(errData[0])
}
}
})
}
resolve(data) {
// 判断返回值的状态
// 1.返回值是promise
//2.返回值是普通的
let rest = this.thenArr.slice(this.count)
if (this.returnText && this.returnText instanceof Promises) {
rest.forEach(item => {
this.returnText.then(item.okCb, item.errCn);
})
return;
} else if(this.returnText) {
this.thenArr[this.count].okCb(this.returnText);
} else {
this.returnText = this.thenArr[this.count].okCb(data);
}
this.count++;
if (this.count < this.thenArr.length) {
this.resolve(data);
}
}
reject(err){
//如果失败，根据count执行当前then函数的失败函数
this.thenArr[this.count].errCn(err)
//如果失败的then函数下面还有未执行的then函数，则直接调用下一个then函数的成功函数
this.count++
if(this.count<this.thenArr.length){
this.resolve()
}
}
then(okCb, errCn) {
this.thenArr.push({
okCb,
errCn
})
return this;
}
}
let pro1=()=>{
return new Promises((resolve,reject)=>{
setTimeout(()=>{
reject(1)
},1000)
})
}
let pro2=()=>{
return new Promises((resolve,reject)=>{
setTimeout(()=>{
reject(2)
},2000)
})
}
Promises.race([pro1(),pro2()]).then((data)=>{
console.log(data)
},(err)=>{
console.log(err+"2344")
})
// new Promises((res, rej) => {
// setTimeout(() => {
// rej(123)
// }, 1000)
// }).then((data) => {
// console.log(data)
// }, (err) => {
// console.log('err', err)
// }).then((data) => {
// return new Promise((res, rej) => {
// res(456)
// })
// }).then((data) => {
// console.log(data)
// })
