A function which generates a random id

generateId.js

(function () {
  var lib = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
  var n = lib.length - 1;

  function generateId(index) {
    var id = [];
    while (index-- > 0) {
      id.push(lib[Math.round(Math.random() * n)]);
    }
    return id.join('');
  }

  if (typeof module === 'object') {
    module.exports = generateId;
  } else if (typeof window === 'object') {
    window.generateId = generateId;
  }
}());