实现一个Promise

最新推荐文章于 2025-07-21 17:46:56 发布

原创最新推荐文章于 2025-07-21 17:46:56 发布 · 247 阅读

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class Promise{
        constructor (fn){
            const _this = this;
            //声明一个等待的队列（重点）
            this._queue = [];
            this._succ_res = null;
            this._error_res = null;
            this.status = "";
            fn(function(...arg){
                _this._succ_res = arg;
                _this.status = "success";
                _this._queue.forEach(json => {
                    json.fn1(...arg);
                });
            },function(...arg){
                _this._error_res = arg;
                _this.status = "error";
                _this._queue.forEach(json => {
                    json.fn2(...arg);
                })
            })
        }
        then(fn1, fn2){
            if(this.status == "success"){
                fn1(this._succ_res);
            } else if(this.status == "error") {
                fn2(this._error_res);
            } else {
                this._queue.push({fn1, fn2});
            }
        }
    }

    Promise.all = function (arr){
        let resArr = [];
        return new Promise((resovle, reject) => {
            let i =0;
            next();
            function next(){
                arr[i].then(res =>{
                    resArr.push(res);

                    i++
                    if(i == res.length) {
                        resolve(resArr);
                    } else {
                        next();
                    }
                }, error =>{
                    reject(error);
                })
            }
        })
    }