下面的例子可返回 checked 属性的 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>蜜蜂教程(mifengjc.com)</title>
  <script>
    function displayResult() {
      var x = document.getElementById("myCheck").defaultChecked;
      alert(x);
    }
  </script>
</head>
<body>

  <form>
    <input type="checkbox" id="myCheck" checked="checked">你喜欢夏天吗?
  </form>
  <button type="button" onclick="displayResult()">选中了默认的选择框吗?</button>

</body>
</html>
        