gistfile1.txt

Function.prototype.cache = function () {
    
    if (this.cache === undefined){
        this.cache = {};
    }
    if (this.cache[arguments[0]] !== undefined){
        console.log("using the cache");
        return this.cache[arguments[0]]; //I wonder why this works even for object arguments (e.g. {test: 3})? Implicity converted to string?
    } 
    else{
        console.log("running method");
        return this.cache[arguments[0]] = this.call(this, arguments[0]);
    }
};

function isPrime( num ) {    
  // everything but 1 can be prime
  var prime = num != 1;
  for ( var i = 2; i < num; i++ ) { 
    if ( num % i == 0 ) { 
      prime = false; 
      break; 
    } 
  }
  return prime; 
} 

console.log(isPrime.cache(524287));
console.log(isPrime.cache(524287));