try{
    if(Promise){}
}
catch (e){
    window.Promise = function(fn) {
        var state = "pending";
        var callbacks = [];
        var result = null;
        function res_rej(a,b,c) {
            if(state!=="pending"){
                return;
            }
            if(b&&b["then"]&&typeof b["then"] === 'function'){
                b["then"](resolve, reject);
                return;
            }
            state = a;
            result = b;
            callbacks.forEach(function (obj) {
                obj[c](result);
            });
        }
        function resolve(value) {
            res_rej("fulfilled",value,0);
        }
        function reject(reason) {
            res_rej("rejected",reason,1);
        }
        this.then = function (onFulfilled,onRejected) {
            return new Promise(function (resolve, reject) {
                switch (state){
                    case "pending":
                        callbacks.push([
                            function () {
                                resolve(onFulfilled(result));
                            },
                            function () {
                                reject(onRejected(result));
                            }
                        ]);
                        break;
                    case "fulfilled":
                        resolve(onFulfilled(result));
                        break;
                    case "rejected":
                        reject(onRejected(result));
                        break;
                }
            });
        };
        this.catch = function (onRejected) {
            return this.then(null, onRejected);
        };
        fn(resolve,reject);
    };
    Promise.resolve = function (value) {
        return new Promise(function(resolve) {
            resolve(value);
        });
    };
    Promise.reject = function (reason) {
        return new Promise(function(resolve, reject) {
            reject(reason);
        });
    };
    Promise.all = function (promises) {
        return new Promise(function(resolve, reject) {
            var count = 0;
            var values = [];
            for (var i = 0; i < promises.length; i++) {
                Promise.resolve(promises[i]).then(function(value) {
                    values.push(value);
                    if (count === promises.length-1) {
                        resolve(values);
                    }
                    else{
                        count++;
                    }
                }, function(reason) {
                    reject(reason);
                });
            }
        });
    };
    Promise.race = function (promises) {
        return new Promise(function(resolve, reject) {
            for (var i = 0; i < promises.length; i++) {
                Promise.resolve(promises[i]).then(function(value) {
                    resolve(value);
                }, function(reason) {
                    reject(reason);
                })
            }
        });
    };
}