Calculate fibonacci numbers

fibonacci.js

// Calculate fibonacci numbers

let fibRec = (n) => {
  if (n<=1) return n;
  return fibRec(n-1) + fibRec(n-2);
}

let mem = [0, 1];
let fibMem = (n) => {
  if (n<=1) return n;
  if (!mem[n]) mem[n] = fibMem(n-1) + fibMem(n-2); 
  return mem[n];
}

fibBine = (n) => {
  let l = (1 + Math.sqrt(5)) / 2;
  let r = (1 - Math.sqrt(5)) / 2;
  return Math.round((Math.pow(l, n) - Math.pow(r, n))/Math.sqrt(5));
}

let logWithTimer = (func, ...rest) => {
  let start = Date.now();
  let res = func.call(null, ...rest);
  console.log("Res: " + res + "; Time: " + (Date.now() - start));
}

let n = 40
logWithTimer(fibRec, n); // 102334155, time 2975 ms
logWithTimer(fibMem, n); // 102334155, time 0 ms
logWithTimer(fibBine, n); // 102334155, time 0 ms