获取 var items= document.getElementsByTagName("p"); 返回数组

node2:/var/www/html/js#cat a17.html 
<p>测试1</p>
<p>测试2</p>
<p>测试3</p>
<p>ggg</p>
<script type="text/javascript" src="jquery-2.2.2.min.js"></script>    
<script type="text/javascript" src="a17.js"></script>
node2:/var/www/html/js#

node2:/var/www/html/js#cat a17.js
var items= document.getElementsByTagName("p");
console.log(items);