How to calculate the amount automatically using javascript

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 .i m new to javascript

You have some inconsistencies with your variable names... nvalue --> nValue. Variable names are case sensitive. — No Results Found
– No Results Found, Commented Sep 16, 2012 at 12:23
No problem, you can delete your question since that's all it was. — No Results Found
– No Results Found, Commented Sep 16, 2012 at 12:38
For javascript development I suggest using firebug and javascript debugger. It would immediately tell you, that nvalue is undefined. — Krzysztof Jabłoński
– Krzysztof Jabłoński, Commented Sep 16, 2012 at 12:50

arok · Accepted Answer · 2012-09-16 13:06:49Z

2

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 ;
    }

edited Sep 16, 2012 at 13:06

arok

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answered Sep 16, 2012 at 12:39

Chris

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Comments

David G · Accepted Answer · 2012-09-16 12:37:01Z

1

Your error is here:

  amount = (nvalue * price);

It should be:

  amount = (nValue * price);

edited Sep 16, 2012 at 12:37

David G

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answered Sep 16, 2012 at 12:35

Jeremy J Starcher

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