<form method=post name=fm>
<select onchange=chg(selectedIndex) name=a>
<option value=亚洲>亚洲
<option value=欧洲>欧洲
<option value=美洲>美洲
</select>
<select name=b>
<option>请选择
</select>
</form>
<script>
var arr=[["中国","日本","朝鲜","新加坡"],["英国","法国","意大利"],["美国","加拿大","巴西"]]
function chg(i){
with(document.fm.b){
length=0;
for(j=0;j<arr[i].length;j++)
options[options.length]=new Option(arr[i][j],arr[i][j])
}
}
chg(0)
</script>
<select onchange=chg(selectedIndex) name=a>
<option value=亚洲>亚洲
<option value=欧洲>欧洲
<option value=美洲>美洲
</select>
<select name=b>
<option>请选择
</select>
</form>
<script>
var arr=[["中国","日本","朝鲜","新加坡"],["英国","法国","意大利"],["美国","加拿大","巴西"]]
function chg(i){
with(document.fm.b){
length=0;
for(j=0;j<arr[i].length;j++)
options[options.length]=new Option(arr[i][j],arr[i][j])
}
}
chg(0)
</script>
<head>
<script languang="javascript">
function mm()
{
var car=new Array(3);
var flower=new Array(3);
var fruit=new Array(3);
var i;
car[0]="宝马";
car[1]="奔驰";
car[2]="东风";
flower[0]="玫瑰";
flower[1]="康乃馨";
flower[2]="菊花";
fruit[0]="banana";
fruit[1]="orange";
fruit[2]="apple";
while(s2.options.length != 0)
s2.remove(0);
if(s1.selectedIndex == 0)
for(i=0;i<fruit.length;i++)
s2.options.add(new Option(fruit[i],i));
else if(s1.selectedIndex == 1)
for(i=0;i<flower.length;i++)
s2.options.add(new Option(flower[i],i));
if(s1.selectedIndex == 2)
for(i=0;i<car.length;i++)
s2.options.add(new Option(car[i],i));
}
</script>
</head>
<body>
<select onChange=mm() name="s1">
<option value=1>水果
<option value=2>花卉
<option value=3>汽车
</select>
<select name="s2">
</select>
</body>
</html>