目地:element.style.样式修改比较消耗性能，下面的方法通过修改类名避免此类情况 添加class ``` function addClass(element,class_name){ element.className+=" "+class_name; } ``` 检测是否含有class ``` function hasClass(element,class_name){ //\b 单词边界 var reg = new RegExp("\\b"+class_name+"\\b"); return reg.test(element.className); } //测试 var banner = document.querySelector('.banner'); console.log(hasClass(banner,"banner")); ``` 删除class ``` function removeClass(element,class_name){ //\b 单词边界 var reg = new RegExp("\\b"+class_name+"\\b"); element.className=element.className.replace(reg,""); } ``` 切换class ``` function toggleClass(element,class_name){ if(hasClass(element,class_name)){ removeClass(element,class_name); }else{ addClass(element,class_name); } } ```