如何通过classname获取DOM节点列表

            function byClassName(className) {
                //高级浏览器
                if(document.getElementsByClassName){
                    return document.getElementsByClassName(className);
                } else {
                    //IE8以下的浏览器
                    var
                        aFit = [];
                        allTag = document.getElementsByTagName('*');
                    for(var i = 0;i<allTag.length; i++){
                        if(allTag[i].className ===className){
                             aFit.push(allTag[i]);
                        }
                    }
                    return aFit;
                }
            }
            console.log(byClassName('action'));