就今天在做一个js的二级级联是我发现使用if,if elseif,和switch进行条件选择时市的结果不一样？

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>
function getCity(){

   var privince=document.getElementById("province");
   var city=document.getElementById('city');

var shu=privince.selectedIndex;
alert(shu);
/*if 语句 - 只有当指定条件为 true 时，使用该语句来执行代码
if...else 语句 - 当条件为 true 时执行代码，当条件为 false 时执行其他代码*/
switch(shu){
   case 1:
     city.options.length=0;
   city.add(new Option("朝阳","朝阳"));
      city.add(new Option("朝阳","朝阳"));
       city.add(new Option("朝阳","朝阳"));
   break;


case 2:

       city.options.length=0;
       city.add(new Option("东莞","东莞"));
       city.add(new Option("东莞","东莞"));
       city.add(new Option("东莞","东莞"));
       break


default:
   city.options.length=0;
       city.add(new Option("辽宁","辽宁"));
          city.add(new Option("辽宁","辽宁"));
           city.add(new Option("辽宁","辽宁"));



}

}
</script>
</head>

<body>
   <FORM METHOD=POST ACTION="" name="form1">
<select name="province" id="province" onchange="getCity()" >
<option selected="selected">请选择所在省份</option>
<option >北京</option>
<option value="广州">广州</option>
<option value="山东">山东</option>

</select>
<select id="city" name="city" >

</select>
</FORM>
</body>
</html>

向日葵一族

浏览 1305回答 1

1回答

随时随地看视频慕课网APP