function to select element even using a numeric class name on IE8

selector.js

    var _selectorRgx = /^(?:#([\w-]+)|(\w+)|\.([\w-]+))$/ ; //stole from jquery, to be used to quicken selector if simple class/id/tag selector used
    
    /**
     * stole the regex logic from jquery, added the support for classname selector starting with a number on IE8
     * for example selector = ".1111" will work with this code even on IE8
     **/
    function select(selector) {     

        var match = _selectorRgx.exec(selector),
            doc = window.document,
            res;

        if (match[1]) {   //id selector
            res = doc.getElementById(match[1]);
        }
        else if (match[3]) { //class selector

            if (doc.getElementsByClassName) {
                res = doc.getElementsByClassName(match[3]);
                res = res[0];
            }
            else {//IE8 - no getElementsByClassName :(

                selector = "." + match[3].replace(/^\d/, function (char) {   //will only replace the first character if its a number with hex so it works
                    return "\\" + char.charCodeAt(0).toString(16) + " ";
                });

                res = doc.querySelector(selector); //selector cant start with a number, its considered invalid
            }
        }
        else if (match[2]) { //tag selector
            res = doc.getElementsByTagName(match[2]);
            res = res[0];
        }
        
        if (!res) {
            res = doc.querySelector(selector);
        }

        return res;
    }