给页面加一个选择了多少门课程

<div style=" font-weight: bold;font-size: 15px;color:#ff0000be;text-align: center;">
    <span v-if="multipleSelection.length == 0">
        请选择课程
    </span>
    <span v-else>
        已选择 {{multipleSelection.length}} 门课程，
    </span>
    <span v-if="priceList[multipleSelection.length] != null">
        <span>
            订单金额：{{(multipleSelection.length * priceList[multipleSelection.length]).toFixed(2)}} 元
        </span>
    </span>
    <span v-else-if="multipleSelection.length > 0">
        订单金额：{{(multipleSelection.length * selGoods.price).toFixed(2)}} 元
    </span>
</div>