RunAwayCache.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)
      return false;

  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: {},

    get(object, property, receiver) {
      if (property == "length")
        return Object.keys(this.cache).length;
    },

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

// This is a known prime
let smartPrime = memoize(isPrime);
let max = 1000000;
let primeCount = 0;
for (let number = 2; number <= max; number++)
  if (smartPrime(number)) {
    primeCount++;
  }

console.log(`Number of primes between 0 and ${max}: ${primeCount}`);

console.log(`Cache memory: ${smartPrime.length}`);

/* Ouput
Number of primes between 0 and 1000000: 78498
Cache memory: 999999
*/