Rounding Off Numbers with JavaScript

★ wanayoo — archive 1999 http://developer.netscape.com/docs/examples/javascript/rounding.html

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Rounding Off Numbers With JavaScript

You can get greater precision presenting floating point numbers with JavaScript. This is important when dealing with large numbers where precision matters. Here's an example which has a generic function roundOff(). This function can round off long numbers in ways you specify.

Here's the code:

<html>
<head><title>Round off Long numbers</title>
<script>
function roundOff(value, precision)
{
        value = "" + value //convert value to string
        precision = parseInt(precision);

        var whole = "" + Math.round(value * Math.pow(10, precision));

        var decPoint = whole.length - precision;

        if(decPoint != 0)
        {
                result = whole.substring(0, decPoint);
                result += ".";
                result += whole.substring(decPoint, whole.length);
        }
        else
        {
                result = whole;
        }
        return result;
}
</script>
</head>

<body>
<h3><center>Testing Rounding off Long floating point
numbers</center></h3>
<form name=myForm>
<pre>
Enter a long number <input type=text name=text1
value=5.199999999999999999 size=20>
Enter precision     <input type=text name=text2 value=2 size=2>
Result              <input type=text name=text3>
</pre>
<center>
<input type=button value=Calculate onClick="myForm.text3.value =
roundOff(myForm.text1.value, myForm.text2.value)">
</center>
</form>
</body>
</html>

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