检测 "Blue" 选项是否默认选中 - 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("blue").defaultChecked;
      alert(x);
    }
  </script>
</head>
<body>

  <form>
    你更喜欢哪种颜色?<br>
    <input type="radio" name="colors" id="red">红色<br>
    <input type="radio" name="colors" id="blue" checked="checked">蓝色<br>
    <input type="radio" name="colors" id="green">绿色
  </form>
  <button type="button" onclick="displayResult()">默认选择蓝色吗?</button>

</body>
</html>
        