Javascript 笔记与总结（2-12）联动菜单

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联动菜单：

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>Document</title>

    <style>

        #div1{

            width: 300px;

            height: 300px;

            background: blue;

            border-bottom: 1px solid black;

        }

    </style>

    <script>

        var area = [

            ['朝阳', '海淀', '昌平'],

            ['九江', '南昌', '赣州']

        ];

        function ld(){

            var select = document.getElementById("province");

            var city = document.getElementById("city");

            var opt = null;

            if(select.value == -1){

                city.innerHTML = opt;

                return;

            }

            for(var i = 0; i < area[select.value].length; i++){

                opt += "<option value="+i+">"+area[select.value][i]+"</option>";

            }

            city.innerHTML = opt;

        }

    </script>

</head>

<body>

    <select name="" id="province" onchange="ld();">

        <option value="-1">请选择</option>

        <option value="0">北京</option>

        <option value="1">江西</option>

    </select>

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

</body>

</html>