页面初加载时：

选择车类型后：

选择车颜色后：

JS实现下拉框的动态添加，网页代码如下：
代码如下:

//给第一个下拉框的SelectChanged时间编码
CarTypeSelect.change(function (){

//取得当前下拉框的值
var CarTypeValue = $(this).val();
//当第一个下拉框内容改变的时候，第三个下拉框要隐藏起来
CarWheelSelect.parent().hide();

if(CarTypeValue !="")
{
CarColorSelect.html("");
$("请选择").appendTo(CarColorSelect);
switch(CarTypeValue){

case "宝马":
var CarColor=["绿色","黑色"];
for(var i = 0;i$("" + CarColor[i] + "").appendTo(CarColorSelect);
}
break;
case "奔驰":
var CarColor = ["白色","红色"];
for(var i = 0;i$("" + CarColor[i] + "").appendTo(CarColorSelect);
}
break;
}
CarColorSelect.parent().show();
}
else
{
CarColorSelect.parent().hide();
}
});

CarColorSelect.change(function (){

var CarColorValue = $(this).val();
CarWheelSelect.html("");
if(CarColorValue != "")
{
CarWheelSelect.html("");
$("请选择").appendTo(CarWheelSelect);
switch(CarColorValue){

case "绿色":
var CarWheel = ["绿钢","绿碳纤维"];
for(var i = 0;i$("" + CarWheel[i] + "").appendTo(CarWheelSelect);
}
break;
case "红色":
var CarWheel = ["红钢","红碳纤维"];
for(var i = 0;i$("" + CarWheel[i] + "").appendTo(CarWheelSelect);
}
break;
case "黑色":
var CarWheel = ["黑钢","黑碳纤维"];
for(var i = 0;i$("" + CarWheel[i] + "").appendTo(CarWheelSelect);
}
break;
case "白色":
var CarWheel = ["白钢","白碳纤维"];
for(var i=0;i$("" + CarWheel[i] + "").appendTo(CarWheelSelect);
}
break;
}
CarWheelSelect.parent().show();
}
else
{
CarWheelSelect.parent().hide();
}
});
});