2019独角兽企业重金招聘Python工程师标准>>> 
<div class="myid1"></div>
<div class="myid2">
<div class="one">1</div>
<div class="two">2</div>
<div class="three">3</div>
</div>
<div class="myid2"></div>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
</ul>
<script type="text/javascript">
var selector = document.querySelector('.myid2');
var selector2 = document.querySelectorAll('.myid2');
console.log(selector);//返回的是单个序号为一DOM元素
console.log(selector2);//返回的是NodeList(节点列表),NodeList不是数组
//像操作Array一样操作NodeList
var arr = [];
var list = document.getElementsByTagName('li');
for(var i =0;i<list.length;i++ ){
var li = list[i];
arr.push(li);
}
console.log(arr);
var selector3 = document.querySelector('.myid2').querySelectorAll('div ');
console.log(selector3);//[div.one, div.two, div.three]
</script>