Generate Random Serial Keys

serial.js

/**
 * Created by Robert Kehoe on 09/06/2014.
 * MIT Licensed.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */


function generateSerialKeys(length, separator) {
  separator = separator || '-';
  var license = new Array(length + 1).join((Math.random().toString(36) + '00000000000000000').slice(2, 18)).slice(0, length);
  return license.toUpperCase().replace(/(\w{4})/g, '$1' + separator).substr(0, length + Math.round(length/4)-1);
}

console.log(generateSerialKeys(24, ' ')); // JXG5 QDER DNXK O6R0 JXG5 QDER
console.log(generateSerialKeys(24));      // QY3R-9Q31-FF5K-A9K9-QY3R-9Q31
console.log(generateSerialKeys(20));      // HJ0A-EUXD-7U95-DN29-HJ0A
console.log(generateSerialKeys(16));      // 41X3-U8D4-SKP2-2O6R

Just what I wanted! Thanks a lot!

Edit: FWIW, I've made an npm package for this, with some modifications.