javascript-->getElementsByClass

    //通过类名获取元素
    //obj->目标元素的上一层元素  cName->目标类名 tagName->目标的标签类型(可缺省)
    function getElementsByClass(obj,cName ,tagName){
           
            var elements = tagName ? obj.getElementsByTagName(tagName) : obj.getElementsByTagName('*');
            var findEles = [ ];
            var reg = new RegExp('^'+cName+'\\s*|\\s+'+cName+'\\s+|\\s+'+cName+'$');
            for(var i=0;i<elements.length;i++) {
                if(reg.test(elements[i].className))findEles.push(elements[i]);          
            }
            return findEles;
        }