javascript too many decimals doing subtractions

Question

I'm doing a simple subtraction with Javascript and the result doesn't match with the real result:

<html>
<head>
    <title></title>
</head>
<body>

<table>
<tr><td>Price: </td><td><input type="text" id="price" value="4500.60" onblur="calculatePrecio();"></td></tr>
<tr><td>Discount: </td><td><input type="text" id="discount" value="500" onblur="calculatePrecio();"></td></tr>
</table>

<div id="divTotalAmount"></div>

<script>

calculatePrecio();

function calculatePrecio()
{
    var price = document.getElementById('price').value;
    var discount = document.getElementById('discount').value;

    p = price;
    d = discount;

    totalAmount = p - d;

    document.getElementById('divTotalAmount').innerHTML = "<h1>"+totalAmount+"</h1>";
}

</script>

</body>
</html>

Can you guys help me? In addition I just don't want to know how to proceed, I want to know the reason for this, if possible.

Perhaps you're wondering: [Is JavaScript's Floating-Point Math Broken?](http://stackoverflow.com/questions/588004/is-javascripts-floating-point-math-broken) — apsillers, Apr 04 '13 at 14:24
Read about floating point arithmetic: http://floating-point-gui.de/ — C. Reed, Apr 04 '13 at 14:26
You can use `.toFixed()`, as the answers suggest, but it's always somewhat perilous to do "money math" with a floating point numeric system. — Pointy, Apr 04 '13 at 14:26

flavian · Accepted Answer · 2017-06-13T07:42:14.913

4

To format the output you can simply used the toFixed method.

var x = 5.3, y = 3;
var z = (x - y).toFixed(2);

HERE is the working jsFiddle.

edited Jun 13 '17 at 07:42

answered Apr 04 '13 at 14:26

flavian

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Thank you for all the anwsers. It's so strange this about "double precision" but I love learning and I'm very interested on this! Thanks! – user1912771 Apr 05 '13 at 06:52

score 1 · Answer 2 · answered Apr 04 '13 at 14:26

1

you can use totalAmount.toFixed(2) for example .... it will be somthing like this xxxxxxxx.xx

answered Apr 04 '13 at 14:26

arnoldrob

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javascript too many decimals doing subtractions

2 Answers2