MemoizeProxy.js

// Check if given number is prime
const isPrime = number => {
  
  if (number < 2) return false;

  // Divide number by all numbers from 2 to sqrt(number)
  // If divisible, then its not a prime
  let div;
  for (div = 2; div <= Math.sqrt(number); div++)
    if (number % div == 0) {
      console.log(`Looped ${div} times`);
      return false;
    }
  console.log(`Looped ${div} times`);
  return true;
}

// Memoize is a Proxy to the actual function
const memoize = fn => new Proxy(fn,

  // Handler with traps
  {
    // We store previous results here
    cache: {},

    // Intercept call to the wrapped function
    apply(target, thisArg, args) {
      // Do we have result in Proxy itself?
      if (!(args in this.cache))
        this.cache[args] = Reflect.apply(target, thisArg, args);
      return this.cache[args];
    }
  }
);

// This is a known prime
let number = 1299827;
const smartPrime = memoize(isPrime);
console.log(`${number} is prime: ${smartPrime(number)}`);
console.log(`${number} is prime: ${smartPrime(number)}`);