all方法.js

Promise.all = function(promises) {
  return new Promise((resolve, reject) => {
    let result = [];
    let index = 0;
    let len = promises.length;
    if(len === 0){
        resolve(result);
        return;
    }
    for(let i = 0;i<len;i++){
        Promise.resolve(promises[i]).then(data =>{
            result[i] = data;
            index ++;
            if(index === len){
                resolve(result);
            }
        }).catch(err=>{
            reject(err);
        })
    }
  });
};


Promise.all = function(promises) {
    return new Promise((resolve,reject) => {
        let len = promises.length;
        let result = [];
        let index = 0;
        if(len === 0){
            resolve(result);
        }
        for(let i = 0;i<len;i++){
            Promise.resolve(promises[i]).then(res=>{
                result[i] = res;
                index ++;
                if(index === len) {
                    resolve(result);
                    return;
                }
            }).catch((err)=>{
                reject(err)
            })
        }
    })
}