store your data in closure scope in order to optimise your functions

Closure101.js

/*
// Slow way without Closure
var ditgitName = function(n) {
  var names = ['zero', 'one', 'two',
               'three', 'four', 'five',
               'six', 'seven', 'eight', 'nine'];
  return names[n]
}

*/

// Closure way
var digitName = (function() {
  var names = ['zero', 'one', 'two',
               'three', 'four', 'five',
               'six', 'seven', 'eight', 'nine'];
  return function(n) {
    return names[n];
  }
}());

alert(digitName(3)); //=> 'three'