fibonachi implementation with backtracking

fib-backtracking.js

const assert = require('assert');

const fib = (n: number, memo?: Array<number>): number => {
  if (memo == null) {
    memo = Array(n);
  }
  if (memo[n] === undefined) {
    memo[n] = n == 0 || n == 1 
      ? 1 
      : fib(n - 1, memo) + fib(n - 2, memo);
  }
  return memo[n];
};

//1,1,2,3,5,8,13

assert.equal(1, fib(0));
assert.equal(1, fib(1));
assert.equal(2, fib(2));
assert.equal(3, fib(3));
assert.equal(5, fib(4));
assert.equal(8, fib(5));
assert.equal(13, fib(6));
assert.equal(3524578, fib(32));
assert.equal(165580141, fib(40));