IE10+ DOMTokenList fix

domtokenlist.js

/**
 * IE 10 + supports ClassList, but the standards are vague. It is extremely
 * convenient to add several classnames at once, FF and Chrome support that.
 *
 * @author Alexander Milevski <[email protected]>
 * 
 * https://gist.github.com/w8r/fbdbfea078629ff913d4
 *
 * MIT License
 *
 * @param  {DOMTokenList} DOMTokenList
 */
(function(DOMTokenList) {
    if (typeof DOMTokenList === 'undefined') {
        return;
    }

    var el = document.createElement('_');
    el.classList.add('a', 'b');

    // duck-typing
    if (el.classList.length !== 2) {
        DOMTokenList.prototype.__add__ = DOMTokenList.prototype.add;
        DOMTokenList.prototype.add = function() {
            for (var i = 0, len = arguments.length; i < len; i++) {
                this.__add__(arguments[i]);
            }
        };

        DOMTokenList.prototype.__remove__ = DOMTokenList.prototype.remove;
        DOMTokenList.prototype.remove = function() {
            for (var i = 0, len = arguments.length; i < len; i++) {
                this.__remove__(arguments[i]);
            }
        };
    }

})(DOMTokenList);