Promise finally and defer polyfill

promise.finally.defer.polyfill.js

/**
 * Promise.prototype.finally
 *
 * Pulled from https://github.com/domenic/promises-unwrapping/issues/18#issuecomment-57801572
 * https://github.com/matthew-andrews/Promise.prototype.finally/blob/master/finally.js
 * @author @stefanpenner, @matthew-andrews
 *
 * Promise.defer
 *
 * Pulled from http://bluebirdjs.com/docs/api/deferred-migration.html
 * @author @cdhowie
 */

(function() {
    // Get a handle on the global object
    var local;
    if (typeof global !== 'undefined') local = global;
    else if (typeof window !== 'undefined' && window.document) local = window;
    else local = self;

    // It's replaced unconditionally to preserve the expected behavior
    // in programs even if there's ever a native finally.
    local.Promise.prototype['finally'] = local.Promise.prototype['finally'] || function (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() {
                    throw reason;
                });
            });
    };
    local.Promise['defer'] = local.Promise['defer'] || function () {
        var result, resolve, reject;
        var self = this;
        return {
            resolve: function (value) {
                if (resolve) {
                    resolve(value);
                } else {
                    result = result || new self(function (r) { r(value); });
                }
            },
            reject: function (reason) {
                if (reject) {
                    reject(reason);
                } else {
                    result = result || new self(function (_, j) { j(reason); });
                }
            },
            promise: new self(function (r, j) {
                if (result) {
                    r(result);
                } else {
                    resolve = r;
                    reject = j;
                }
            })
        };
    };
}());