promise-polyfill.js

(function (global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined' ? factory() :
        typeof define === 'function' && define.amd ? define(factory) :
            (factory());
}(this, (function () {
    'use strict';

    /**
     * @this {Promise}
     */
    function finallyConstructor(callback) {
        var constructor = this.constructor;
        return this.then(
            function (value) {
                return constructor.resolve(callback()).then(function () {
                    return value;
                });
            },
            function (reason) {
                return constructor.resolve(callback()).then(function () {
                    return constructor.reject(reason);
                });
            }
        );
    }

// Store setTimeout reference so promise-polyfill will be unaffected by
// other code modifying setTimeout (like sinon.useFakeTimers())
    var setTimeoutFunc = setTimeout;

    function noop() {
    }

// Polyfill for Function.prototype.bind
    function bind(fn, thisArg) {
        return function () {
            fn.apply(thisArg, arguments);
        };
    }

    /**
     * @constructor
     * @param {Function} fn
     */
    function Promise(fn) {
        if (!(this instanceof Promise))
            throw new TypeError('Promises must be constructed via new');
        if (typeof fn !== 'function') throw new TypeError('not a function');
        /** @type {!number} */
        this._state = 0;
        /** @type {!boolean} */
        this._handled = false;
        /** @type {Promise|undefined} */
        this._value = undefined;
        /** @type {!Array<!Function>} */
        this._deferreds = [];

        doResolve(fn, this);
    }

    function handle(self, deferred) {
        while (self._state === 3) {
            self = self._value;
        }
        if (self._state === 0) {
            self._deferreds.push(deferred);
            return;
        }
        self._handled = true;
        Promise._immediateFn(function () {
            var cb = self._state === 1 ? deferred.onFulfilled : deferred.onRejected;
            if (cb === null) {
                (self._state === 1 ? resolve : reject)(deferred.promise, self._value);
                return;
            }
            var ret;
            try {
                ret = cb(self._value);
            } catch (e) {
                reject(deferred.promise, e);
                return;
            }
            resolve(deferred.promise, ret);
        });
    }

    function resolve(self, newValue) {
        try {
            // Promise Resolution Procedure: https://github.com/promises-aplus/promises-spec#the-promise-resolution-procedure
            if (newValue === self)
                throw new TypeError('A promise cannot be resolved with itself.');
            if (
                newValue &&
                (typeof newValue === 'object' || typeof newValue === 'function')
            ) {
                var then = newValue.then;
                if (newValue instanceof Promise) {
                    self._state = 3;
                    self._value = newValue;
                    finale(self);
                    return;
                } else if (typeof then === 'function') {
                    doResolve(bind(then, newValue), self);
                    return;
                }
            }
            self._state = 1;
            self._value = newValue;
            finale(self);
        } catch (e) {
            reject(self, e);
        }
    }

    function reject(self, newValue) {
        self._state = 2;
        self._value = newValue;
        finale(self);
    }

    function finale(self) {
        if (self._state === 2 && self._deferreds.length === 0) {
            Promise._immediateFn(function () {
                if (!self._handled) {
                    Promise._unhandledRejectionFn(self._value);
                }
            });
        }

        for (var i = 0, len = self._deferreds.length; i < len; i++) {
            handle(self, self._deferreds[i]);
        }
        self._deferreds = null;
    }

    /**
     * @constructor
     */
    function Handler(onFulfilled, onRejected, promise) {
        this.onFulfilled = typeof onFulfilled === 'function' ? onFulfilled : null;
        this.onRejected = typeof onRejected === 'function' ? onRejected : null;
        this.promise = promise;
    }

    /**
     * Take a potentially misbehaving resolver function and make sure
     * onFulfilled and onRejected are only called once.
     *
     * Makes no guarantees about asynchrony.
     */
    function doResolve(fn, self) {
        var done = false;
        try {
            fn(
                function (value) {
                    if (done) return;
                    done = true;
                    resolve(self, value);
                },
                function (reason) {
                    if (done) return;
                    done = true;
                    reject(self, reason);
                }
            );
        } catch (ex) {
            if (done) return;
            done = true;
            reject(self, ex);
        }
    }

    Promise.prototype['catch'] = function (onRejected) {
        return this.then(null, onRejected);
    };

    Promise.prototype.then = function (onFulfilled, onRejected) {
        // @ts-ignore
        var prom = new this.constructor(noop);

        handle(this, new Handler(onFulfilled, onRejected, prom));
        return prom;
    };

    Promise.prototype['finally'] = finallyConstructor;

    Promise.all = function (arr) {
        return new Promise(function (resolve, reject) {
            if (!arr || typeof arr.length === 'undefined')
                throw new TypeError('Promise.all accepts an array');
            var args = Array.prototype.slice.call(arr);
            if (args.length === 0) return resolve([]);
            var remaining = args.length;

            function res(i, val) {
                try {
                    if (val && (typeof val === 'object' || typeof val === 'function')) {
                        var then = val.then;
                        if (typeof then === 'function') {
                            then.call(
                                val,
                                function (val) {
                                    res(i, val);
                                },
                                reject
                            );
                            return;
                        }
                    }
                    args[i] = val;
                    if (--remaining === 0) {
                        resolve(args);
                    }
                } catch (ex) {
                    reject(ex);
                }
            }

            for (var i = 0; i < args.length; i++) {
                res(i, args[i]);
            }
        });
    };

    Promise.resolve = function (value) {
        if (value && typeof value === 'object' && value.constructor === Promise) {
            return value;
        }

        return new Promise(function (resolve) {
            resolve(value);
        });
    };

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

    Promise.race = function (values) {
        return new Promise(function (resolve, reject) {
            for (var i = 0, len = values.length; i < len; i++) {
                values[i].then(resolve, reject);
            }
        });
    };

// Use polyfill for setImmediate for performance gains
    Promise._immediateFn =
        (typeof setImmediate === 'function' &&
            function (fn) {
                setImmediate(fn);
            }) ||
        function (fn) {
            setTimeoutFunc(fn, 0);
        };

    Promise._unhandledRejectionFn = function _unhandledRejectionFn(err) {
        if (typeof console !== 'undefined' && console) {
            console.warn('Possible Unhandled Promise Rejection:', err); // eslint-disable-line no-console
        }
    };

    /** @suppress {undefinedVars} */
    var globalNS = (function () {
        // the only reliable means to get the global object is
        // `Function('return this')()`
        // However, this causes CSP violations in Chrome apps.
        if (typeof self !== 'undefined') {
            return self;
        }
        if (typeof window !== 'undefined') {
            return window;
        }
        if (typeof global !== 'undefined') {
            return global;
        }
        throw new Error('unable to locate global object');
    })();

    if (!('Promise' in globalNS)) {
        globalNS['Promise'] = Promise;
    } else if (!globalNS.Promise.prototype['finally']) {
        globalNS.Promise.prototype['finally'] = finallyConstructor;
    }

})));