我试图用一个下拉菜单，一个乘数应用到预定数量。下面是HTML代码，但我在jQuery的经验不足。
<body>
<span class="Door">
<select name="Amount" class="wpcf7-form-control wpcf7-select">
<option value="1.1">Traditional_doors</option>
<option value="1.1">Duo_doors</option>
<option value="1.3">cottage_doors</option>
<option value="1.4">Modern_doors</option>
<option value="1.4">Diamante_doors</option>
<option value="1.5">Handmade_shaker_doors</option>
<option value="1.6">Beaded_classic_or_victorian_doors</option>
</select>
</spa>获取的选择上的变化值，与数相乘并打印
var a = 10;
$('select').change(function() {
a = a * $(this).val();
console.log(a);
a=10;
})<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<body>
<span class="Door">
<select name="Amount" class="wpcf7-form-control wpcf7-select">
<option value="1.1">Traditional_doors</option>
<option value="1.1">Duo_doors</option>
<option value="1.3">cottage_doors</option>
<option value="1.4">Modern_doors</option>
<option value="1.4">Diamante_doors</option>
<option value="1.5">Handmade_shaker_doors</option>
<option value="1.6">Beaded_classic_or_victorian_doors</option>
</select>
</span>