document.getElementsByClassName = function (cl) {
    var retnode = [];
    var myclass = new RegExp('\\b' + cl + '\\b');
    var elem = this.getElementsByTagName('*');
    for (var i = 0; i < elem.length; i++) {
        var classes = elem[i].className;
        if (myclass.test(classes)) retnode.push(elem[i]);
    }
    return retnode;
};