如何使用JavaScript自动计算金额

Question

This is my function

function  doMath() { 
   var counter; var nvalue; var amount;
   var price=100;
   nValue = document.getElementById("message").value;
   amount=(nvalue*price);
   document.getElementById("total").value=amount ;
}

My html

<input type="" name="message" id="message" onkeyup="doMath()"maxlength="60">message
<input type="text" name="total" id="total" maxlength="60"> amount

when user enter value into message field it should calculate the amount automatically and show it in amount field.

but while i entering the value it show NAN

its not calculating can anyone help me how to fix this .im new to javascript

Answer 1

You declared your variable as nvalue but used nValue instead.

   function  doMath() { 
       var nValue; var amount;
       var price=100;
       nValue = document.getElementById("message").value;
       amount=(nValue*price);
       document.getElementById("total").value=amount ;
    }

Answer 2

Your error is here:

  amount = (nvalue * price);

It should be:

  amount = (nValue * price);