实现Promise.all Promise.race

Promise.all = (promises) => {

    let results=[];

    return new Promise((resolve,reject)=>{

        let i=0;

        while(i

            promises[i].then(res=>{

                results.push(res);

                i++;

                if(i===promises.length){resolve(results);}

            }).catch(err=>{

                reject(err); //只要有任何Promise出现reject，Promise.newAll就直接reject

            });

        }

    })

}

如果想捕获promise.all的错误又想返回怎么办

手写Promise.All，并且在这个All中加一个超时时间

1、使用setTimeout方式，在一个promise.all中设置。

2、将setTimeout封装成promise，然后使用promise.race来输出最快的promise

---

实现Promise.race

Promise.race = function(promises){

    return new Promise((resolve,reject) => {

        let i=0;

        while(i

            promises[i].then(res=>{

                resolve(res); //出现第一个被resolve的直接resolve

            }).catch(err=>{

                reject(err); //出现第一个被reject的直接reject

            });

            i++;

        }

    })

}

js实现并发多个请求，返回先得到response的，类似Promise.race的实现

---

要求1：按以下要求输出

human('Jack').eat().sleep(5).go().rest(10);

// I am Jack

// Eat

// 等 5 秒

// Sleep 5s

// Go

// 等 10 秒

// Rest 10s

要求2：eat/sleep/go/rest可以改变任意顺序human('Jack').sleep(5).eat().rest(10).go();

function human(name){

    return new Human(name)

}

function Human(name）{

    this.name=name

    this.sayHello()

    this.queue=Promise.resolve()

}

Human.prototype.sayHello=function(){

    console.log(`I am ${this.name}`)

}

Human.prototype.eat=function(){

    this.queue = this.queue.then(()=>{

        return new Promise((resolve)=>{

            console.log('Eat') 

            resolve()})

        })

        return this

}

Human.prototype.sleep=function(time){

    this.queue=this.queue.then(()=>{

        return new Promise((resolve)=>{

            setTimeout(()=>{

            console.log(`Sleep ${time}s`)

            resolve()},time*1000)

        })

    })

    return this

}

Human.prototype.go=function(){

    this.queue=this.queue.then(()=>{

        return new Promise((resolve)=>{

            console.log('Go')

            resolve()

        })

    })

    return this

}

Human.prototype.rest=function(time){

    this.queue=this.queue.then(()=>{

        return new Promise((resolve)=>{

            setTimeout(()=>{

            console.log(`Rest ${time}s`);

            resolve()},time*1000)

        })

    })

    return this

}

human('Jack').eat().sleep(5).go().rest(10);

---

function cancelableXHR(URL){

    var req=newXMLHttpRequest();

    var promise=new Promise((resolve,reject)=>{

        req.open('GET',URL,true);

        req.onload=function(){

            if(req.status===200){resolve(req.responseText);}

            else{reject(new Error(req.statusText));}

        };

        req.onerror=function(){reject(new Error(req.statusText));};

        req.onabort=function(){reject(new Error('abort this request'));};

        req.send();

    });

    var abort=function(){

        if(req.readyState!==XMLHttpRequest.UNSENT){req.abort();}

    };

    return{

        promise:promise,

        abort:abort

    };

}