乘形式值

Question

<form> 
Chapter 1 - Please enter how many copys you would like <br> 
<input type="text" id="chap1"> <br><br> 
Chapter 2 - Please enter how many copys you would like <br> 
<input type="text" id="chap2"> <br><br> 
Chapter 3 - Please enter how many copys you would like <br> 
<input type="text" id="chap3"> <br><br> 
Chapter 4 - Please enter how many copys you would like <br> 
<input type="text" id="chap4"> <br><br> 
Chapter 5 - Please enter how many copys you would like <br> 
<input type="text" id="chap5"> <br><br> 
    <b> Total price : <output id = "total"> 0 </output> </b> 

我試圖創建一個網站中，你可以通過章節訂購的書籍，每章花費£2。我需要它將單個表格的值乘以2，然後在輸出中顯示此成本。我想用java腳本來做到這一點，而不是jQuery。

我還沒有嘗試過很多，因爲我無法找到很多關於這個問題，所以任何指針在正確的方向將不勝感激。

感謝

Answer 1

function calc(){ 
    price = 2; 
    fields = document.querySelectorAll("input[id^='chap']"); 
    tot = 0; 
    for(i=0; i<fields.length; i++){ 
     tot += fields[i].value * price; 
    } 
    document.getElementById("total").innerHTML = tot; 
} 

這是一個簡單的例子，你就可以改善

Answer 2

fiddle link

<input type="text" id="chap1"> 
<input type="text" id="chap2"> 
<input type="text" id="chap3"> 
<input type="text" id="chap4"> 
<input type="text" id="chap5"> 
<b> Total price : <output id = "total"> 0 </output> </b> 
<button onclick="myFunction()">Click me</button> 
<script> 
function myFunction() { 
var text1= document.getElementById("chap1").value; 
var text2= document.getElementById("chap2").value; 
var text3= document.getElementById("chap3").value; 
var text4= document.getElementById("chap4").value; 
var text5= document.getElementById("chap5").value; 
var total=parseInt(text1)+parseInt(text2)+parseInt(text3)+parseInt(text4)+parseInt(text5); 
document.getElementById("total").innerHTML = total*2.1; 
} 
</script>