memoize.js

const memoize = (func) => {
  const memo = new Map()
  return (...args) => {
    const key =  JSON.stringify(args)
    if (!memo.has(key)) memo.set(key, func(...args))
    return memo.get(key)
  }
}

/*
const factorial = memoize((n) => {
  if (n === 0) return 1
  return n * factorial(n - 1)
})

factorial(5)
factorial(6)

const fibonacci = memoize((n) => {
  if (n < 1) return 0
  if (n === 1) return 1
  return fibonacci(n - 2) + fibonacci(n - 1)
})

for (let i = 0; i < 21; i ++) {
  console.log(fibonacci(i))
}
*/