Caching Wrapper.js

Caching Wrapper.js

// Part 1.
// Implement a function prototype extension that caches function results for
// the same input arguments of a function with one parameter.
//
// For example:
// Make sin(1) have the result of Math.sin(1), but use a cached value
// for future calls.
//
// Part 2.
// Use this new function to refactor the code example.
// Some good test numbers: 524287, 9369319, 2147483647 (all primes)

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;
} 

Function.prototype.makeCacheable = function() {
    originalMethod = this;
    if (!('cache' in originalMethod)) {
        originalMethod.cache = {}
    }
    
    return function(arg) {
        if (arg in originalMethod.cache) {
            console.log('cached');
        }
        else {
            console.log('not cached');
            originalMethod.cache[arg] = originalMethod(arg);            
        }
        
        return originalMethod.cache[arg];
    }
};

console.log(isPrime(524287));
console.log(isPrime(9369319));
console.log(isPrime(2147483647));

isPrime = isPrime.makeCacheable();

console.log(isPrime(524287));
console.log(isPrime(9369319));
console.log(isPrime(2147483647));

console.log(isPrime(524287));
console.log(isPrime(9369319));
console.log(isPrime(2147483647));