6.1 选择并转移导航菜单

表单选择器，选择改变即跳转页面；
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script>
        window.onload = initForm;
        function initForm() {
            document.getElementById("area").selectedIndex = 0;
            document.getElementById("area").onchange = jumpPage;
        }
        function jumpPage() {
            var newLoc = document.getElementById ("area");
            var newPage = newLoc.options [newLoc.selectedIndex].value;
            if (newPage != "") {
                window.location = newPage;
            }
        }
    </script>
</head>
<body>
<form action="" id="myForm">
    <select id="area">
        <option selected>杭州</option>
        <option>上海</option>
    </select>
</form>
</body>
</html>