Enhancing Element.setAttribute() to accept only 1 argument for attribute creation

Element.setAttribute.enhanced.js

//test case http://jsfiddle.net/NHZ6W/
(function(Element, undefined){
    var _setAttribute = Element.prototype.setAttribute;
 
    Element.prototype.setAttribute = function(attrName, attrValue){
        if (this.hasAttribute(attrName)) {
            if (attrValue !== undefined) {
                _setAttribute.call(this, attrName, attrValue);
            }
            //do nothing if attr exists and action is to create
        }
        else {
            _setAttribute.call(this, attrName, (attrValue === undefined ? '' : attrValue));
        }
    }
})(Element);