fibonacci-memoization.js

// Simple unoptimized calculator for the nth fibonacci number.
const fibonacci = n => (n <= 1 ? n : fibonacci(n - 1) + fibonacci(n - 2))

console.time('fibonacci')
console.log(fibonacci(20))
console.timeEnd('fibonacci')

// A single argument function memoization wrapper.
const memoize = func => {
  const cache = {}
  return arg => (arg in cache) ? cache[arg] : (cache[arg] = func(arg))
}

// Apply memoization to the fibonacci function.
const memoizedFibonacci = memoize(fibonacci)

console.time('memoizedFibonacci')
console.log(memoizedFibonacci(20))
console.timeEnd('memoizedFibonacci')