Javascript 显示按比例的会员数量

Javascript to display pro-rata membership amount

我负责维护我的非营利性游泳俱乐部的网站;它由 Squarespace 托管,我们的财务主管要求我在 membership page 中添加一个计算器,以便潜在会员在希望一次性付款时可以轻松计算所需的按比例金额。如果按年支付,一整年的费用为 475 英镑,因此如果在 6 月 30 日单击该按钮,我预计页面上的价格为 return 237.50 英镑。查看其他一些答案并使用我有限的 Javascript 知识,我想出了这个,但它并没有给我我期望的答案:

<!DOCTYPE html>
<html>
<body>

<p>Click the button to display the total pro-rata annual amount due, if membership starts tomorrow</p>

<button onclick="myFunction()">Click Me</button>

<p id="prorata"></p>

<script>
function myFunction() {
    var today = new Date();
    var totalDays = new Date(today.getFullYear(), today.getMonth(), 0).getDate();
    var daysLeft = (totalDays - today.getDate()) - 1; 
    var pricePerDay = 1.30;
    var n = daysLeft * pricePerDay;
    document.getElementById("prorata").innerHTML = n;
}
</script>

</body>
</html>

非常感谢任何帮助!

这是你想要的吗?? 我喜欢这样:remaining_Days =(今年最后一天 - 今天);

按比例 = remaining_Days * 1.30;

<!DOCTYPE html>
<html>
<body>

<p>Click the button to display the total pro-rata annual amount due, if membership starts tomorrow</p>

<button onclick="myFunction()">Click Me</button>

<p id="prorata"></p>

<script>
function myFunction() {
    
    var today = new Date();
    var year = new Date().getFullYear();
  
var oneDay = 24*60*60*1000; // hours*minutes*seconds*milliseconds
var firstDate = new Date();

var secondDate = new Date(year,11,31);

var diffDays = Math.round(Math.abs((firstDate.getTime() - secondDate.getTime())/(oneDay)));

    var n = diffDays* 1.30;
    document.getElementById("prorata").innerHTML = n;
}
</script>

</body>
</html>