我有一個 jQuery .change 的小問題，當我點擊數據時，數據沒有改變。我正在使用 ddSlick。我想達到的效果是這樣的：http://www.convertmymoney.com/ - 因此，當輸入金額時，數據已經另外改變，當有人輸入金額并更改貨幣（標志）時，它也會改變數據，不幸的是我的情況并非如此。$(document).ready(function() {  var total = 0;  $("#amountin, #amountout,#amountValue").on("change", function() {    cal();  });    $("#amountValue").on("keydown", function() {    cal();  });  $("#exchange").on("click", function() {    var amountinval = $("#amountin").val();    var amountoutval = $("#amountout").val();    cal();  });  function cal() {    var amountinval = $("#amountin").val();    var amountoutval = $("#amountout").val();    var amountValue = $("#amountValue").val();    total = parseFloat(amountValue * (amountinval / amountoutval)).toFixed(2);    $('#totavalue').attr('placeholder', total);  }});<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script><div class="currency-calc-in__input currency-calc__input col-lg-8 col-sm-6 col-md-6 col-6">  <label for="amountValue" class="currency-calc__label">Kwota (posiadam)</label>  <input type="number" class="form-control" id="amountValue" name="amountValue" aria-describedby="numberHelp" placeholder="100"></div><select class="custom-select currency-calc-in__slick" id="amountin" name="amountin">  <option value="1" data-description="PLN" data-value="1" data-symbol="PLN">Polski z?oty</option>  <option value="0.1286" data-description="THB" data-value="0.1286" data-symbol="THB">Bat tajlandzki</option>  <option value="4.1886" data-description="USD" data-value="4.1886" data-symbol="USD">Dolar amerykański</option>  <option value="2.6503" data-description="AUD" data-value="2.6503" data-symbol="AUD">Dolar australijski</option>  <option value="0.5406" data-description="HKD" data-value="0.5406" data-symbol="HKD">Dolar Hongkongu</option></select>