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Editorial Team
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Asked: 2026-06-14T17:31:59+00:00

I have this simple script, i want to multiply Var a * Var b

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I have this simple script, i want to multiply Var a * Var b then Multiply this by Var C with a set number eg 15.

But it doesn’t seem to work?

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>

<script>
$('input[name="box2"]').keyup(function() {
    var a = $('input[name="box1"]').val();
    var b = $(this).val();
    var c = $(15).val();
    $('input[name="box3"]').val(a * b * c);
});
​
</script>
</head>


<body>
<input name="box1" type="text" /><br />
<input name="box2" type="text" /><br />
<input name="box3" type="text" />
</body>
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1 Answer

  1. Editorial Team

    A few changes to do :

    var a = parseInt($('input[name="box1"]').val(), 10);
var b = parseInt($(this).val(), 10);
var c = 15; // really no need to try to build a dom element to get an int

    Beware never never use parseInt without specifying the radix (parseInt("09") is 0...).

    Another problem in your code is that you try to build your jquery collection before the dom is ready. Use this :

    <script>
$(function(){
   $('input[name="box2"]').keyup(function() {
     var a = $('input[name="box1"]').val();
     var b = $(this).val();
     var c = $(15).val();
     $('input[name="box3"]').val(a * b * c);
   });
});
</script>

    Note that it’s also best practice, especially when using jQuery which makes it easy, to have a script element at the end of the body to keep all the javascript that isn’t in separate files.

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