Scratch

MoreGamesNow · 2011-01-20 22:02:58

Want to test a prime number below 92,819,543,569 (9 billion)? Just copy this javascript that I wrote... well, all except the addCommas function. It makes a list of primes and uses it to check. If it is taking forever to load, look for "var cont=100" and set it to a lower number; you'll have a smaller range of primes you can check, but it will load faster. The text-boxes show you stats about the list. Click the button to check a number.

Copy the code into Notepad on a PC or Textedit on a Mac.

IMPORTANT: As always, replace the green ) with two of these: )

P.S. My phone number is prime smile

Update: Got rid of the green ), so just copy and paste it into Textedit/Notepad, save it as Name.html, and then open the HTML document.

<HTML>
<HEAD>
<TITLE>
Prime
</TITLE>
<SCRIPT TYPE="text/javascript">

function addCommas(nStr)
{
nStr += '';
x = nStr.split('.');
x1 = x[0];
x2 = x.length > 1 ? '.' + x[1] : '';
var rgx = /(\d+)(\d{3})/;
while (rgx.test(x1)) {
x1 = x1.replace(rgx, '$1' + ',' + '$2');
}
return x1 + x2;
}

var PrimeList = new Array();

function primelist(n)
{
PrimeList = [2,3,5]

var test=6;
var i=0;
var sq=3;
var k;
var add;
var cont=100;
var sqt=1;

for(i=0; i<cont; i++)
{
for(test=test; test<(PrimeList[i+1]*PrimeList[i+2]); test++)
{
add = true
for(k=0; k<=i; k++)
{
if(test%PrimeList[k]==0)
{
add=false;
}
}
if(add)
{
if(sq*sq==test)
{
sqt++;
sq=PrimeList[sqt]
}
else
{
PrimeList.push(test);
}
}
}
}
return PrimeList
}

function pr (n)
{
if(n==1 || n==0)
{
alert(n+" is not prime")
}
else
{
var i;
var j = Math.sqrt(n);
var k = true;

for(i=0; PrimeList[i]<=j; i++)
{
if(n%PrimeList[i]==0)
{
k=false;
break;
}
}
if(k)
{
alert("Prime")
}
else
{
alert(n +" is not prime, it is divisible by "+ PrimeList[i])
}
}
}
</SCRIPT>
</HEAD>
<BODY onLoad="document.na.prime.value=primelist(); document.na.len.value=PrimeList.length; document.na.hig.value=PrimeList[PrimeList.length-1]; alert('Loaded');">
<form name="na">
List:<input type="text" size="100" name="prime"><BR>
Length:<input type="text" size="6" name="len"><BR>
Last Item:<input type="text" size="6" name="hig"><BR>
<input type="button" value="Check Number" onClick="var mm = document.na.hig.value; pr(prompt('Number > 0 and < '+(addCommas(mm*mm) ) ) );">
</form>
</BODY>
</HMTL>

Last edited by MoreGamesNow (2011-01-31 16:50:45)

Scratch

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#1 2011-01-20 22:02:58

Really fast Prime Number checker (under 9 billion)

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