JavaScript numberFormat(), formatFileSize

gistfile1.js

var Utility = {

  getBitRate = function(size, duration) {
    return numberFormat(Math.round((size * 8) / duration));
  },
  
  numberFormat = function(x) {
    return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
  },
  
  formatFileSize = function(size) {
    if (isNaN(size)) return 'NaN';

    decr   = 1024;
    step   = 0;
    suffix = ['b', 'KiB', 'MiB', 'GiB'];

    while ((size / decr) > 0.9) {
      size = size / decr;
      step ++;
    }
    
};