factorial_with_memoization.js

const factorial = num => (num > 1 ? num * factorial(num - 1) : 1)

const memoize = fn => {
  const cache = {}
 
  // with multiple arguments
  //   return (...args) => {
  //     const key = JSON.stringify(args)
  //     return key in cache ? cache[key] : cache[key] = fn.apply(null, args)
  //   }
  
  return num => num in cache ? cache[num] : cache[num] = fn(num)
}
  
const memoizedFactorial = memoize(factorial)

console.log(`factorial(7)=${factorial(7)}`)
console.log(`factorial(4)=${factorial(4)}`)
console.log(`factorial(7)=${factorial(7)}`)