js 获取 input value
引用：http://foolraty.blog.163.com/blog/static/366588962010250721581/
<html>
<head></head>
<body>
<input type="text" id="123" name="213" value="2"/>
<script>
alert("111");
var a = document.getElementsByName("213")[0].value
alert(a);
</script>
</body>
</html>
