如何使用javascript數據表單while（）？

Question

我有這樣的代碼

<script> 
function select(val, item) 
{ 
var prize = $(".prize"+item).val(); 
var prize = prize*val; 
$(".dollar"+item).html(prize); 

//----- THIS CODE ERROR --------// 
$sub_total=$(".dollar1").val()+$(".dollar2").val()+$(".dollar3").val()+..... etc; 
$(".total").html($sub_total); 
// ---------------------------- // 

} 
</script> 

<input type="hidden" value="140" class="prize1"> 
<select class="quantity" id="quant2" value="1" onchange="select(this.value, 1)"> src="1"> 
<option value="1" selected>1</option> 
<option value="2">2</option> 
<option value="3">3</option> 
</select> 
prize : <span class="dollar1" value="140">140</span> 
<br> 
<input type="hidden" class="prize2" value="150"> 
<select class="quantity" id="quant2" value="2" onchange="select(this.value, 2)"> src="2"> 
<option value="1">1</option> 
<option value="2" selected>2</option> 
<option value="3">3</option> 
</select> 
prize : <span class="dollar2" value="300">300</span> 

...... etc 

<br><br> 
<label> TOTAL </label> : <span class="total">?????</span> 

如何使總元素，可以計算在價格上的所有款項？如果我在onchange選擇後，然後在dollar1 dollar2 dollar3 ... etc將 總結，因爲我在這個腳本上使用while()。 這個腳本應該怎麼做？

$sub_total=dollar1+dollar2+dollar3+..... etc; 
$(".total").html($sub_total); 

IF這個PHP代碼

<?php 
while($loll = $resultu->fetch_array(MYSQLI_BOTH)){ 
$id_item= $loll['id_item']; 
$prize=$loll['prize']; 
    <input type="hidden" value="<?php echo $prize ?>" class="prize<?php echo $id_item ?> "> 
    <select class="quantity" value="<?php echo $id_item ?>" onchange="select(this.value, <?php echo $id_item ?>)"> src="<?php echo $id_item ?>"> 
    <option value="1" selected>1</option> 
    <option value="2">2</option> 
    <option value="3">3</option> 
    </select> 
    prize : <span class="dollar<?php echo $id_item ?>" value="<?php echo $prize ?>"><?php echo $prize ?></span> 
    <br> 
} 
    ...... etc 

    <br><br> 
    <label> TOTAL </label> : <span class="total">?????</span> 

我怎樣才能求和$sub_total= ALL --> $(".dollar<?php echo $id_item ?>")?

Answer 1

下面是當用戶改變選擇元素將運行一個求和計算一個簡單的jQuery例子：

HTML

<select id="select1"> 
      <option value="1">1</option> 
      <option value="2">2</option> 
      <option value="3">3</option> 
     </select> 
     <select id="select2"> 
      <option value="1">1</option> 
      <option value="2">2</option> 
      <option value="3">3</option> 
     </select> 
     <input id="result" type="text"/> 

的JavaScript

$(document).ready(function() { 
    $('#select1, #select2').change(function() { 
     var num1 = Number($('#select1').val()); 
     var num2 = Number($('#select2').val()); 
     var sum = num1 + num2; 
     $('#result').val("$" + sum); 
    }); 

});