Fibonacci

fibonacci.ts

// using phi - best performance
// see: https://akuli.github.io/math-tutorial/fib.html
function fibonacciGoldenRation(n: number) {
  const phi = (1 + Math.sqrt(5))/2;
  const asymptotic = Math.pow(phi, n) / Math.sqrt(5);
  return Math.round(asymptotic);
}

// using for() loop
const fibonacciForLoop = (num: number) => {
  var sequence = [0, 1];
  for (let position = 2; position < num + 1; position++) {
    sequence[position] = sequence[position - 1] + sequence[position - 2];
  }
  return sequence[num];
};

// using recursion - very poor performance 
// just (console.log(num) and you'll see why)
const fibonacciRecursive = (num: number): number => {
  if (num === 0) return 0;
  if (num <= 2) return 1;
  return fibonacciRecursive(num - 1) + fibonacciRecursive(num - 2);
};