js如何获取只class为a的元素，不包括.a.b的元素

Question

js如何获取只class为a的元素，不包括.a.b的元素？
例如：

<div class="a b"></div><div class="a"></div>

Answer 1

&nbsp; &nbsp; &nbsp; &nbsp; var elems = document.getElementsByTagName("div");&nbsp; &nbsp; &nbsp; &nbsp; var arr = [];&nbsp; &nbsp; &nbsp; &nbsp; for(var i = 0,len = elems.length;i<len;i++){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if(elems[i].className.indexOf("a")>=0&&elems[i].className.indexOf("b")<0){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; arr.push(elems[i]);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; alert(arr.length);