获取DOM元素的三种方法

 1 <!doctype html>
 2 <html lang="en">
 3  <head>
 4   <meta charset="UTF-8">
 5   <meta name="Generator" content="EditPlus®">
 6   <meta name="Author" content="">
 7   <meta name="Keywords" content="">
 8   <meta name="Description" content="">
 9   <title>获取DOM元素的三种方法</title>
10  </head>
11  <body onload="getElement()">
12     <script type="text/javascript">
13         function getElement(){
14             //getElementsByTagName根据标签名
15             var a=document.getElementsByTagName("input")
16             alert(a.length)//4
17             //getElementsByName根据name值
18             var b=document.getElementsByName("aihao")
19             alert(b.length)//3
20             //getElementById根据id值
21             var c=document.getElementById("c")
22             alert(c.value)
23 
24         }
25     </script>
26     <input type="checkbox" name="aihao" value="001">抽烟<br>
27     <input type="checkbox" name="aihao" value="002">喝酒<br>
28     <input type="checkbox" name="aihao" value="003">烫头<br>
29     <input type="text" id="c" name="c" value="004">
30   
31  </body>
32 </html>