phpjs/functions/math/decbin.js

php.js offers community built php functions in javascript

function decbin(number) {
  // From: http://phpjs.org/functions
  // +   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);
}