phpjs/functions/math/decbin.js

php.js offers community built php functions in javascript

function decbin(number) {
  //  discuss at: http://phpjs.org/functions/decbin/
  // original by: Enrique Gonzalez
  // bugfixed by: Onno Marsman
  // improved by: http://stackoverflow.com/questions/57803/how-to-convert-decimal-to-hex-in-javascript
  //    input by: pilus
  //    input by: nord_ua
  //   example 1: decbin(12);
  //   returns 1: '1100'
  //   example 2: decbin(26);
  //   returns 2: '11010'
  //   example 3: decbin('26');
  //   returns 3: '11010'

  if (number < 0) {
    number = 0xFFFFFFFF + number + 1;
  }
  return parseInt(number, 10)
    .toString(2);
}