菜鸟教程在线编辑器

 
                <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<form id="myForm" action="/">
  name: <input type="text" name="fname" value="RUNOOB"><br>
  url: <input type="text" name="lname" value="www.runoob.com"><br>
  <input type="submit" value="提交按钮">
</form> 

<p>点击按钮获取 form 表单中第一个（索引为 0）元素的值。</p>

<button onclick="myFunction()">点我</button>

<p id="demo"></p>

<script>
function myFunction() {
  var x = document.getElementById("myForm").elements.namedItem("fname").value;
  document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>
              