js split正则

Question

 求解我用字表达式  
    var data="asdfasdf<span>aa</span>asdfasdf"
        var regValue=/(<span\s?[^\>]*>.*?<\/span>)/gi    
         var data= data.split(regValue)
可以切割成["asdfasdf"，"<span>aa</span>","asdfasdf"]  的效果
不用（）就不行 为什么 

Answer 1

我试了一下，发现 加不加括号都只能分割成["asdfasdf","asdfasdf"]