tail call recursion optimization for factorial and fibonacci

recursion.js

'use strict';

const factorial = n => n < 2 ? 1 : n * factorial(n - 1)

// run with --harmony and "use strict" to optimize tail call recursion
const factorialOptimizedTailRecursion = (n, acc = 1) => n < 2 ? acc : factorialOptimizedTailRecursion(n - 1, acc * n)

const n = 100000000

// console.log(factorial(n)) // RangeError: Maximum call stack size exceeded
console.log(factorialOptimizedTailRecursion(n)) // Infinity






// 1 1 2 3 5 8 13 21 34 55

const fibonacci = n => n < 2 ? 1 : fibonacci(n - 1) + fibonacci(n - 2)

const fibonacciOptimizedTailRecursion = (n, acc = 1) => n < 2 ? acc : fibonacciOptimizedTailRecursion(n - 1, fibonacciOptimizedTailRecursion(n - 2, acc + 1))

const fibonacciOptimizedMemoization = (n, acc = {}) => acc[n] ? acc[n] : acc[n] = n < 2 ? 1 : fibonacciOptimizedMemoization(n - 1, acc) + fibonacciOptimizedMemoization(n - 2, acc)

const arr = [10,11,12,13,14,15,16,17,18,19,45]

console.log(arr.map(n => fibonacciOptimizedMemoization(n))) // works immediately

console.log(arr.map(n => fibonacci(n))) // works too long

console.log(arr.map(n => fibonacciOptimizedTailRecursion(n))) // works even a bit longer