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@maxbucknell
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Last active Dec 29, 2015
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Generate an array containing the prime factorisation of a positive integer.

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function(
x // The positive integer to factorise
, i // An index
, r // The array of results
) {
r=[]; // Initialise the array
for(;x>=2;) { // Anything less than 2 should be ignored, since there is no valid prime factorisation other than the empty array
for(i=2;x%i;++i); // Starting at 2, we iterate, searching for a new factor. Note that a new factor is guaranteed to be prime, because any composite number has a prime factor less than it, which will have already been caught.
r.push(i); // When we find a factor, the loop terminates, and we append this value
x/=i // Run the whole thing again with the new factor removed
}
return r // Fin.
}
function(x,i,r){r=[];for(;x>=2;){for(i=2;x%i;++i);r.push(i);x/=i}return r}
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
Version 2, December 2004
Copyright (C) 2011 YOUR_NAME_HERE <YOUR_URL_HERE>
Everyone is permitted to copy and distribute verbatim or modified
copies of this license document, and changing it is allowed as long
as the name is changed.
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. You just DO WHAT THE FUCK YOU WANT TO.
{
"name": "primeFactorisation",
"description": "Splits an integer into an array of its prime factors in ascending order.",
"keywords": [
"math",
"prime",
"factorization"
]
}
<!DOCTYPE html>
<title>Prime Factorisation of Positive Integers</title>
<div>Expected value: <b>6857</b></div>
<div>Actual value: <b id="ret"></b></div>
<script>
// From Project Euler question 3
// The prime factors of 13195 are 5, 7, 13 and 29.
// What is the largest prime factor of the number 600851475143 ?
var primeFactor = function(x,i,r){r=[];for(;x>=2;){for(i=2;x%i;++i);r.push(i);x/=i}return r}
document.getElementById( "ret" ).innerHTML = primeFactor(600851475143).slice(-1)[0];
</script>
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