下拉框联动示例-优快云博客

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>

    <style>
            select{
                width: 100px;
                float: left;
                margin-right: 10px;
            }
        </style>
</head>
<body>
    <select name="" id="may01">
        <option value="0">请选择省份</option>
        <option value="四川">四川</option>
        <option value="云南">云南</option>
        <option value="贵州">贵州</option>
    </select>
    <select name="" id="may02"></select>
    <select name="" id="may03"></select>

    <script>
        var may01 = document.getElementById("may01");
        var may02 = document.getElementById("may02");
        var may03 = document.getElementById("may03");

        may01.onchange=function(){
            var val = this.value;
           if(val=='四川'){
               var sichuan=["成都市","绵阳市","乐山市"];
               var str="<option value='0'>"+"请选择城市"+"</option>";
               for(var i=0;i<sichuan.length;i++){
                   str+='<option value="'+sichuan[i]+'">'+sichuan[i]+'</option>'
               }
               may02.innerHTML=str
           }
        };
        may02.onchange=function(){
            var val=this.value;
            if(val=="成都市"){
                var chengdu=["青羊区","锦江区","武侯区"];
                var str="<option value='0'>"+"请选择城市"+"</option>";
                for(var i=0;i<chengdu.length;i++){
                    str+='<option value="'+chengdu[i]+'">'+chengdu[i]+'</option>'
                }
                may03.innerHTML=str
            }else{
                may03.innerHTML=""
            }
        }      
        
    </script>
</body>
</html>