if (!String.prototype.startsWith) {
    String.prototype.startsWith = function(search, pos) {
        pos = !pos || pos < 0 ? 0 : +pos;
        return this.substring(pos, pos + search.length) === search;
    };
}

if (!String.prototype.endsWith) {
    String.prototype.endsWith = function(search, this_len) {
        if (this_len === undefined || this_len > this.length) {
            this_len = this.length;
        }
        return this.substring(this_len - search.length, this_len) === search;
    };
}

if (!Object.assign) {
    Object.defineProperty(Object, 'assign', {
        enumerable: false,
        configurable: true,
        writable: true,
        value: function(target, firstSource) {
            'use strict';
            if (target === undefined || target === null) {
                throw new TypeError('Cannot convert first argument to object');
            }

            var to = Object(target);
            for (var i = 1; i < arguments.length; i++) {
                var nextSource = arguments[i];
                if (nextSource === undefined || nextSource === null) {
                    continue;
                }

                var keysArray = Object.keys(Object(nextSource));
                for (var nextIndex = 0, len = keysArray.length; nextIndex < len; nextIndex++) {
                    var nextKey = keysArray[nextIndex];
                    var desc = Object.getOwnPropertyDescriptor(nextSource, nextKey);
                    if (desc !== undefined && desc.enumerable) {
                        to[nextKey] = nextSource[nextKey];
                    }
                }
            }
            return to;
        }
    });
}