Oct 15, 2009

memoried function

 Function.prototype.memorized = function(key) {
     this._values = this._values || {};

     if (this._values[key] !== undefined) {
         return this._values[key]
     }
     else {
         //"this" is parent function object
         this._values[key] = this.apply(this, arguments); /* the "this" passed as context object is optional? */
         return this._values[key];
     }
 };


 function isPrime(num) {
     alert(this);
     var prime = num != 1;
     for (var i = 2; i < num; i++) {
         if (num % i == 0) {
             prime = false;
             break;
         }
     }
     return prime;
 }

 var a = isPrime.memorized(5);
 alert(a);
 var b = isPrime.memorized(5);
 alert(b);