getElementsByClassName that supports native browser implementation

get-elements-by-classname.js

if (typeof RIV === 'undefined' || !RIV)  {
    var RIV = {};
}

RIV.utils = (function() {
    return {
        /**
         * Gets all the DOM elements that have a specified className. Uses the native browser function if it exists.
         * @param {string} classname The classname you want to search for
         * @param {string} node A selector to select the scope. Defaults to "document" if not specified.
         * @return {Array} classElements Array of items with the classname in the scope of node
         */
        getElementsByClassName: function(classname, node) {
            node = node || document;
            if (node.getElementsByClassName) {
                return node.getElementsByClassName(classname);
            } else {
                var classElements = new Array(),
                    els = node.getElementsByTagName("*"),
                    pattern = new RegExp("(^|\\s)"+classname+"(\\s|$)");
                for (var i = 0, j = 0, elsLen = els.length; i < elsLen; i++) {
                    if ( pattern.test(els[i].className) ) {
                        classElements[j] = els[i];
                        j++;
                    }
                }
                return classElements;
            }
        }
    };
})();
//RIV.utils.getElementsByClassName("class");