​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>请从列表中选择一辆新车。</p>
​
<select id="mySelect" onchange="myFunction()">
  <option value="Audi">Audi</option>
  <option value="BMW">BMW</option>
  <option value="Mercedes">Mercedes</option>
  <option value="Volvo">Volvo</option>
</select>
​
<p>当您选择一辆新车时，会触发一个函数，输出所选汽车的值。</p>
​
<p id="demo"></p>
​
<script>
function myFunction() {
  var x = document.getElementById("mySelect").value;
  document.getElementById("demo").innerHTML = "You selected: " + x;
}
</script>
​
</body>
</html>
​