Editing Comparison of memoization implementations

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Preparation code

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<script>
  
  
  //memo1
  //underscore.js implem
  
  function memoize1(func, hasher) {
      var memo = {};
      hasher || (hasher = function(value){
        return value; //^this could be done better..surely..
      });
      return function() {
        var key = hasher.apply(this, arguments);
        return hasOwnProperty.call(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
      };
    };
  
  
  //memoize.js - by @addyosmani, @philogb, @mathias
  // with a few useful tweaks from @DmitryBaranovsk
  function memoize2( fn ) {
  	return function () {
  		var args = Array.prototype.slice.call(arguments),
  		hash = "",
  		i  = args.length,
  		currentArg = null;
  		while(i--){
  			currentArg = args[i];
  			hash += (currentArg === Object(currentArg)) ?
  				JSON.stringify(currentArg) : currentArg;
  		}
  		fn.memoize || (fn.memoize = {});
  		return (hash in fn.memoize) ? fn.memoize[hash] :
  			fn.memoize[hash] = fn.apply( this , args );
  	};
  } 
  
  //memo4 - by stevenlevithan
  function memoize4(functor, expiration) {
  	var memo = {};
  	return function () {
  		var key = Array.prototype.join.call(arguments, "§");
  		if (key in memo)
  			return memo[key];
  		if (expiration)
  			setTimeout(function () {delete memo[key];}, expiration);
  		return memo[key] = functor.apply(this, arguments);
  	};
  }
  
//@abozhilov
//Based on the @stevenlevithan memoize4 version
function memoize8(fn) {
    var memo = {};
    return function () {
        var key = [].join.call(arguments, '§') + '§';
        return (key in memo) ? memo[key] : memo[key] = fn.apply(this, arguments);
    };              
}
  
  var fib, fiborg;
  fiborg = fib = function (x) {
      if(x < 2) return 1; else return fib(x-1) + fib(x-2);
  }
  
</script>

Include JavaScript libraries as follows: <script src="//cdn.ext/library.js"></script>

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Code snippets to compare

Test 1

Title

Async (check if this is an asynchronous test)

Code

fib = memoize8(fiborg);
fib(20);

Test 2

Title

Async (check if this is an asynchronous test)

Code

fib = memoize2(fiborg);
fib(20);

Test 3

Title

Async (check if this is an asynchronous test)

Code

fib = memoize4(fiborg);
fib(20);

Test 4

Title

Async (check if this is an asynchronous test)

Code

fib = memoize8(fiborg);
fib(20);