The sieve of eratosthenes

JavaScript/HTML

<html>
<!--
        Written by Jeff Mikels (http://jeff.mikels.cc),
        borrowing heavily from the Python version at
        http://badcomputer.org/code/eratos/python1.bot
-->
<script language="javascript">

function sieve(x) {
        y = Math.floor(Math.sqrt(x));
        var a = new Array();

        a.push(2);
        for (i = 3; i <= x; i+=2) {
                a.push(i)
        }
        a.reverse();
        var primes = new Array();
        while ((current_prime = a.pop()) <= y) {
                primes.push(current_prime);
                for (index in a) {
                        if (a[index] % current_prime == 0) {
                                a.splice(index,1);
                        }
                }
        }
        primes.push(current_prime);
        a.reverse();
        primes = primes.concat(a);
        return primes.join(' ');
}

function dosieve() {
        input_value = document.getElementById('input').value;
        document.getElementById('output').innerHTML = sieve(input_value);
}
</script>
<!-- INPUT AND OUTPUT -->
<p>I will find all primes up to the number you enter here...
<br />
        <input type=text id=input name=input value="" onchange="dosieve();"/>
        <button onclick="dosieve();"/>click here</button>
<p>Your primes...
<br /><div id="output" style="width:100%"></div>
</html>

Run it!

I will find all primes up to the number you enter here...

Your primes...

back to Eratosthenes page

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This page, and all pages on this site were created and are maintained by Darren Kirby using valid XHTML 1.0 and CSS, and are ©copyright 2002 - 2008. The Penguin image was created by Tukka, and is used by permission. Inspiration for the look of this site was provided by Eric A. Meyer's CSS gallery. This website runs on Gentoo Linux. It is served by Apache. PHP and MySQL hold together the backend.

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