摘要：試圖寫了一下大概測試了一下沒有用專業的測試工具測試代碼感覺還是寫的比較好懂的，本人水平較差，如果測試有問題，歡迎回復指出地址同一執行隊列中原生是先于實現的自己實現暫時用模擬必須傳入并且構造狀態改變之后傳遞的值執行之后返回的這里必須異步處理否

試圖寫了一下,大概測試了一下,沒有用專業的測試工具測試....

代碼感覺還是寫的比較好懂的，本人水平較差，如果測試有問題，歡迎回復指出
地址： https://github.com/julyL/Code...

(function(global) {
    function isFunction(val) {
        return typeof val == "function";
    }

    function isObject(val) {
        return typeof val == "object";
    }

    function asyncExcute(fn) {
        return function() {
            setTimeout(fn); // 同一執行隊列中,原生Promise是先于setTimeout實現的,自己實現暫時用setTimeout模擬
        }
    }
    function Promise(fn) {
        if (!isFunction(fn) || this instanceof Promise == false) {
            throw new TypeError("Promise必須傳入function并且new構造")
        }
        this.status = "pending";
        this.value = undefined; //  promise狀態改變之后傳遞的值
        this.thenPromise = undefined; //執行then之后返回的promise
        this.resolveQueue = []; //
        this.rejectQueue = []; //   
        var re = asyncExcute(function(resolveData) { this._resolve(resolveData) }.bind(this)), //這里必須異步處理,否則then函數執行以前可能就已經執行了_resolve,但這時then中函數還未加入resolveQueue中
            rj = asyncExcute(function(resolveData) { this._reject(resolveData) }.bind(this));
        try {
            fn(re, rj)
        } catch (error) {
            this.status = "reject";
            this.value = error;
            asyncExcute(function(){this._reject(error)});         //  new Promise(()=>{ 出現異常... }).then(refn,rjfn);    出現異常時then還未執行, rjfn還未加入到rejectQueue中  
        }
    }
    Promise.prototype.then = function(refn, rjfn) {
        var returnPro = new Promise(function() {});
        this.thenPromise = returnPro;
        this.resolveQueue.push(refn);
        this.rejectQueue.push(rjfn);

        if (this.status == "resolve") { //執行then時,如果狀態已經不是pending,則執行相應函數
            this._resolve(this.value);
        }
        if (this.status == "reject") {
            this._reject(this.value);
        }
        return returnPro;
    }
    Promise.prototype._resolve = function(resolveData) {
        var handle,
            returnVal;
        this.status = "resolve";
        this.value = resolveData;
        while (this.resolveQueue.length > 0) { //2.2.6  當 promise 成功執行時，所有 onFulfilled 需按照其注冊順序依次回調
            handle = this.resolveQueue.shift();
            if (!isFunction(handle)) { //不是函數  2.1.1 onFulfilled 不是函數，其必須被忽略
                this.thenPromise.value = resolveData;
                this.thenPromise.status = "resolve";
                this.thenPromise._resolve();
                return;
            }
            try { //如果 onFulfilled 或者 onRejected 拋出一個異常 e ，則 promise2 必須拒絕執行，并返回拒因 e
                returnVal = handle(resolveData);
            } catch (error) {
                this.thenPromise.status = "reject";
                this.thenPromise.value = error;
                this.thenPromise._reject();
            }
            if (isObject(returnVal || isFunction(returnVal))) { //如果返回值為對象或者函數
                if (returnVal == this.thenPromise) { //如果 promise 和 x 指向同一對象，以 TypeError 為據因拒絕執行 promise
                    this.thenPromise.status = "reject";
                    this.thenPromise.value = new TypeError("[[Resolve]](promise, x),promise 和 x 不能指向同一對象");
                } else if (returnVal instanceof Promise) { //如果 x 為 Promise ，則使 promise 接受 x 的狀態
                    try {
                        then.call(returnVal, this.thenPromise._resolve.bind(this.thenPromise), this.thenPromise._reject.bind(this.thenPromise));
                    } catch (error) {
                        this.thenPromise.status = "reject";
                        this.thenPromise.value = error;
                        this.thenPromise._reject();
                    }
                } else { //如果 x 為對象或者函數
                    try { //如果取 x.then 的值時拋出錯誤 e ，則以 e 為據因拒絕 promise
                        var then = returnVal.then;
                        if (isFunction(then)) {
                            then.call(returnVal, this.thenPromise._resolve.bind(this.thenPromise), this.thenPromise._reject.bind(this.thenPromise));
                        }
                    } catch (error) {
                        this.thenPromise.status = "reject";
                        this.thenPromise.value = error;
                        this.thenPromise._reject();
                    }
                }
            } else {
                this.thenPromise.value = returnVal;
                this.thenPromise.status = "resolve";
                this.thenPromise._resolve();
            }
        }
    }

    Promise.prototype._reject = function(resolveData) {
        var handle,
            returnVal;
        this.status = "resolve";
        this.value = resolveData;
        while (this.rejectQueue.length > 0) {     //2.2.6  當 promise 成功執行時，所有 onFulfilled 需按照其注冊順序依次回調
            handle = this.rejectQueue.shift();
            if (!isFunction(handle)) {          //不是函數  2.1.1 onFulfilled 不是函數，其必須被忽略
                this.thenPromise.value = resolveData;
                this.thenPromise.status = "resolve";
                this.thenPromise._resolve();
                return;
            }
            try { //如果 onFulfilled 或者 onRejected 拋出一個異常 e ，則 promise2 必須拒絕執行，并返回拒因 e
                returnVal = handle(resolveData);
            } catch (error) {
                this.thenPromise.status = "reject";
                this.thenPromise.value = error;
                this.thenPromise._reject();
            }
            if (isObject(returnVal || isFunction(returnVal))) { //如果返回值為對象或者函數
                if (returnVal == this.thenPromise) { //如果 promise 和 x 指向同一對象，以 TypeError 為據因拒絕執行 promise
                    this.thenPromise.status = "reject";
                    this.thenPromise.value = new TypeError("[[Resolve]](promise, x),promise 和 x 不能指向同一對象");
                } else if (returnVal instanceof Promise) { //如果 x 為 Promise ，則使 promise 接受 x 的狀態
                    try {
                        then.call(returnVal, this.thenPromise._resolve.bind(this.thenPromise), this.thenPromise._reject.bind(this.thenPromise));
                    } catch (error) {
                        this.thenPromise.status = "reject";
                        this.thenPromise.value = error;
                        this.thenPromise._reject();
                    }
                } else {      //如果 x 為對象或者函數
                    try {     //如果取 x.then 的值時拋出錯誤 e ，則以 e 為據因拒絕 promise
                        var then = returnVal.then;
                        if (isFunction(then)) {
                            then.call(returnVal, this.thenPromise._resolve.bind(this.thenPromise), this.thenPromise._reject.bind(this.thenPromise));
                        }
                    } catch (error) {
                        this.thenPromise.status = "reject";
                        this.thenPromise.value = error;
                        this.thenPromise._reject();
                    }
                }
            } else {
                this.thenPromise.value = returnVal;
                this.thenPromise.status = "resolve";
                this.thenPromise._resolve();
            }
        }
    }

    Promise.resolve = function(value) {
        return new Promise(function(re, rj) {
            re(value)
        })
    }
    Promise.reject = function(value) {
        return new Promise(function(re, rj) {
            re(value)
        })
    }
    Promise.all = function(queue) {
        if (Object.prototype.toString.call(queue) != "[object Array]") {
            return;
        }
        var returnPromise = new Promise(function() {}),
            resolveNum = 0;
        for (var i = 0; i < queue.length; i++) {
            queue[i].then(function() {
                resolveNum++;
                if (resolveNum == queue.length) {
                    returnPromise._resolve();
                }
            });
        }
        return returnPromise;
    }
    Promise.race = function(queue) {
        if (Object.prototype.toString.call(queue) != "[object Array]") {
            return;
        }
        var returnPromise = new Promise(function() {}),
            resolveNum = 0;
        for (var i = 0; i < queue.length; i++) {
            queue[i].then(function() {
                returnPromise._resolve();
            });
        }
        return returnPromise;
    }
    global.Promise = Promise;
})(window);