通过另外一个下拉菜单已选选项来修改当前下拉菜单的选项。 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>蜜蜂教程(mifengjc.com)</title>
  <script>
    var carsAndModels = {};
    carsAndModels['VO'] = ['V70', 'XC60', 'XC90'];
    carsAndModels['VW'] = ['Golf', 'Polo', 'Scirocco', 'Touareg'];
    carsAndModels['BMW'] = ['M6', 'X5', 'Z3'];

    function ChangeCarList() {
      var carList = document.getElementById("car");
      var modelList = document.getElementById("carmodel");
      var selCar = carList.options[carList.selectedIndex].value;
      while (modelList.options.length) {
        modelList.remove(0);
      }
      var cars = carsAndModels[selCar];
      if (cars) {
        for (var i = 0; i < cars.length; i++) {
          var car = new Option(cars[i], i);
          modelList.options.add(car);
        }
      }
    }
  </script>
</head>
<body onload="ChangeCarList();">

  <select id="car" onchange="ChangeCarList();">
  <option value="">-- Car --</option>
  <option value="VO">Volvo</option>
  <option value="VW">Volkswagen</option>
  <option value="BMW">BMW</option>
</select>
  <select id="carmodel"></select>

</body>
</html>
        