​x
 
<!DOCTYPE html>
<html>
<body>
​
<h1>演示如何访问 OPTGROUP 元素</h1>
​
<select size="4">
  <optgroup id="myOptgroup" label="Chinese cars">
    <option value="byd">BYD</option>
    <option value="geely">GEELY</option>
    <option value="gwm">GWM</option>
  </optgroup>
</select>
​
<p>单击按钮可获取选项组的标签/说明。</p>
​
<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
​
<script>
function myFunction() {
  var x = document.getElementById("myOptgroup").label;
  document.getElementById("demo").innerHTML = x;
}
</script>
​
</body>
</html>
​