memoize a function to only fire once.

once.js

var once = function(func) {
  var alreadyCalled = false;
  return function() {
    if (!alreadyCalled) {
      func.apply(this, arguments);      
      alreadyCalled = true;
    }
  };
};

To 'memoize' a function pass it as parameter into function 'once'.
For instance:

var say = function(what) {
  console.log(what)
}

var sayonce = once(say); // => returns memoized version of function say

sayonce('what') // => will console log 'what'
sayonce('no more') // => will not fire again