{"id":1054,"date":"2012-05-11T17:05:30","date_gmt":"2012-05-11T23:05:30","guid":{"rendered":"http:\/\/bateru.com\/news\/?p=1054"},"modified":"2018-07-01T23:06:00","modified_gmt":"2018-07-02T05:06:00","slug":"code-of-the-day-javascript-prime-factors-of-a-number","status":"publish","type":"post","link":"https:\/\/bateru.com\/news\/2012\/05\/code-of-the-day-javascript-prime-factors-of-a-number\/","title":{"rendered":"Code of the Day: Javascript, Prime Factors of a Number"},"content":{"rendered":"

Javascript: Prime Factorization<\/b>
\n<\/a>
\nToday’s code is a enhancement of Code Renaissance<\/a>‘s version of “Finding Prime Numbers in Javascript”.
\nMain difference are the following.<\/p>\n

    \n
  1. Faster performance by eliminating recursion and caching Math.sqrt.<\/li>\n
  2. Whole numbers bigger than 1 return an empty array, since they’re not prime numbers.<\/li>\n
  3. Decimal values are converted to whole numbers.<\/li>\n<\/ol>\n

    <\/p>\n

    \r\n\/**\r\n* @author Larry Battle - http:\/\/bateru.com\/news\/contact-me\r\n* @date May 11, 2012\r\n* @license MIT and GPL v3\r\n* @purpose Return the prime factors of a number.\r\n* @info - http:\/\/bateru.com\/news\/?s=prime+factors\r\n*\/\r\nvar getPrimeFactors = function(num) {\r\n    num = Math.floor(num);\r\n    var root, factors = [], x, sqrt = Math.sqrt, doLoop = 1 < num;\r\n    while( doLoop ){\r\n        root = sqrt(num);\r\n        x = 2;\r\n        if (num % x) {\r\n            x = 3;\r\n            while ((num % x) && ((x += 2) < root));\r\n        }\r\n        x = (x > root) ? num : x;\r\n        factors.push(x);\r\n        doLoop = ( x != num );\r\n        num \/= x;\r\n    }\r\n    return factors;\r\n}\r\n<\/pre>\n
    <\/code><\/p>\n
    Example:<\/b>
    \ngetPrimeFactors(15120) \/\/ returns [2, 2, 2, 3, 3, 3, 7]<\/p>\n
    Demo:<\/b>
    \n