}
//添加一个Class
function addClass(element,className){
if(!hasClass(element,className)){
element.className+=' '+className;
}
}
//删除一个Class
function removeClass(element,className){
if(hasClass(element,className)){
element.className=element.className.replace
(new RegExp('(\s|^)'+className+'(\s|$)'),' ');
}
}