promise相关

promise

let FULFILLED= 'fulfilled';
let REJECT = 'reject';
let PENDING = 'pending';
class Promise1{
    constructor(excutor){
        let that = this;
        that.status = PENDING;
        that.value = null;
        that.reason = null;
        that.onFulfilledCallbacks = [];
        that.onRejectedCallbacks = [];
        let resolve = function(value){
            if(that.status == PENDING){
                that.status = FULFILLED;
                that.value = value;
                that.onFulfilledCallbacks.map((cb)=>cb())
            }
        }
        let reject = function(reason){
            if(that.status == PENDING){
                that.status = REJECT;
                that.reason = reason;
                that.onRejectedCallbacks.map((cb)=>cb());
            }
        }
        try{
            excutor(resolve,reject);
        }catch(e){
            reject(e);
        }

    }
    then(onFulfilled,onRejected){
        let that = this;
        if(that.status==FULFILLED){
            onFulfilled(that.value);
        }
        if(that.status==REJECT){
            onRejected(that.reason);
        }
        if(that.status==PENDING){
            that.onFulfilledCallbacks.push(()=>{
                onFulfilled(that.value);
            })
            that.onRejectedCallbacks.push(()=>{
                onRejected(that.reason);
            })
        }
    }
}

let promise = new Promise1((resolve,reject)=>{
    resolve('1');
    setTimeout(()=>{
        
        console.log('time')
    },0)
})
promise.then((value)=>{
    console.log('2',value);
},()=>{
    console.log('3');
})
promise.then(()=>{
    console.log('4')
    setTimeout(()=>{
        console.log('lalal')
    },1000)
}) // 1 2 4 time lalal

Promise.all1 = function(values){
    return new Promise((resolve,reject)=>{
        let arr = [];
        for(let i=0;i<values.length;i++){
            let cur = values[i];
            if(isPromise(cur)){
                cur.then((data)=>{
                    processData(i,data);
                },reject)
            }else{
                processData(i,cur);
            }
        }
        let processData = (key,value)=>{
            arr[key] = value;
            if(++key == values.length){
                resolve(arr);
            }
        }
    })
}
let p1 = new Promise((resolve, reject) => {
    resolve('成功了')
  })
  
  let p2 = new Promise((resolve, reject) => {
    resolve('success')
  })
  
  let p3 = Promise.reject('失败')
  
  Promise.all1([p1, p2]).then((result) => {
    console.log(result)               //['成功了', 'success']
  }).catch((error) => {
    console.log(error)
  })
  
  Promise.all1([p1,p3,p2]).then((result) => {
    console.log(result)
  }).catch((error) => {
    console.log(error)      // 失败了，打出 '失败'
  })

promise.race

function isPromise(x){
    if(typeof x === 'function' || (typeof x === 'object' && x!=null)){
        return true;
    }
    return false;
}
Promise.race1 = function(values){
    return new Promise((resolve,reject)=>{
        for(let i=0;i<values.length;i++){
            if(isPromise(values[i])){
                values[i].then(resolve,reject);
            }else{
                resolve(values[i]);
            }
        }
    })
}
  Promise.race1([p1, p2]).then((result) => {
    console.log(result)               //成功了
  }).catch((error) => {
    console.log(error)
  })
  
  Promise.race1([p3,p2]).then((result) => {
    console.log(result)
  }).catch((error) => {
    console.log(error)     //失败
  })

promise.finally

Promise.resolve = function(value){
    return new Promise((this.resolve,reject)=>{
        resolve(value);
    })
}

Promise.prototype.finally = function(callback){
    return this.then((data)=>{
        return Promise.resolve(callback()).then(()=>data);
    },err=>{
        return Promise.resolve(callback().then(()=>{throw err}));
    })
}

promise.catch

Promise.prototype.catch = function(callback){
    return this.then(null,callback);
}