// noprotect

​

function fib1(n) {

  if(n <= 2) {

    return 1;

  } else {

    var a = fib1(n - 1);

    var b = fib1(n - 2);

    return a + b;

  }

}

​

// https://en.wikipedia.org/wiki/Call_stack#Structure

​

function fib2(n) {

  var fiber = { arg: n, returnAddr: null, a: 0 /* b is tail call */ };

  rec: while (true) {

    if (fiber.arg <= 2) {

      var sum = 1;

      while (fiber.returnAddr) {

        fiber = fiber.returnAddr;

        if (fiber.a === 0) {

          fiber.a = sum;

          fiber = { arg: fiber.arg - 2, returnAddr: fiber, a: 0 };

          continue rec;

        }

        sum += fiber.a;

      }

      return sum;

    } else {

      fiber = { arg: fiber.arg - 1, returnAddr: fiber, a: 0 };

    }

  }

}

​

var p = performance;

​

var c = 33;

​

for (var i = 0; i < 10; i++) {

  fib1(c);

  fib1(c);

  fib2(c);

  fib2(c);

}

​

fib1(c);

console.log('result stack', fib1(c));

fib2(c);

console.log('result fiber', fib2(c));

​

var s1 = p.now();

fib1(c);

var e1 = p.now();

​

var s2 = p.now();

fib2(c);

var e2 = p.now();

​

console.log('stack', e1 - s1);

console.log('fiber', e2 - s2);

​

​

var s1 = p.now();

fib1(c);

var e1 = p.now();

​

var s2 = p.now();

fib2(c);

var e2 = p.now();

​

console.log('stack', e1 - s1);

console.log('fiber', e2 - s2);