gistfile1.js

/* Generates a memoizable getter. */
Object.prototype.memoize = function(key, func) {
  var __key__ = "__" + key + "__";
  this.__defineGetter__(key, function() {
    if (this[__key__]) return this[__key__];
    this[__key__] = func();
    return this[__key__];
  });
};


/***********/
/* Example */
/***********/
var n = {};
n.memoize('ichi', function() { 
  console.log("Setting to 1");
  return 1; 
});

console.log(n.ichi);
> Setting to 1
> 1
console.log(n.ichi);
> 1