问我想使用amount_t属性添加这些金额。并在文本框中显示

EN

<input type="checkbox" name="subject1" value="course_id" amount_t="amount"  class="amount" />
<input type="checkbox" name="subject2" value="course_id" amount_t="amount"  class="amount" />
<input type="checkbox" name="subject3" value="course_id" amount_t="amount"  class="amount" />
<input type="checkbox" name="subject4" value="course_id" amount_t="amount"  class="amount" />

$(document).ready(function() {
  $(".amount").change(function() {
    if (($(this).is(':checked'))) {
      var res;
      var val1 = parseInt($(this).attr("amount_t"));
      var val2 = $("#amount").attr("value");
      console.log('value1', val1);
      console.log('value2', val2);
      res = val2.slice(-4);
      res = parseInt(res);
      var val3 = 'Amount : $ ';
      var val4 = val1 + res;
      var val = val3 + val4;
      $("#amount").val(val);
    } else {
      var res;
      var val1 = parseInt($(this).attr("amount_t"));
      var val2 = $("#amount").attr("value");
      console.log('value1', val1);
      console.log('value2', val2);
      res = val2.slice(-4);
      res = parseInt(res);
      var val3 = 'Amount : $ ';
      var val4 = res - val1;
      var val = val3 + val4;
      $("#amount").val(val);
    }
  });

});

<input type="text" name="amount" id="amount" class="form-control frm" value="Amount : $ 0000" disabled>