Untitled

#!/usr/bin/env node

// usage:
// $ time ./fibonacci.js 40
// 0.  40 :  165580141
// 0.  40 :  165580141
// 5ms 3259ms
//
// real     0m3.310s
// user     0m3.301s
// system   0m0.017s

//fibonacci(40)
//fibonacci2(40)

function fibonacci(n) {
  var res;
  if (fibonacci.stack[n]) return fibonacci.stack[n];
  if (n < 2)
    res = 1;
  else
    res = fibonacci(n - 2) + fibonacci(n - 1);

  return (fibonacci.stack[n] = res);
}
fibonacci.stack = {};

function fibonacci2(n) {
  if (n < 2) return 1;
  return fibonacci2(n - 2) + fibonacci2(n - 1);
}

function  fibonacci3(n) {
  n = n || 1;
  var t = 1, i = 1, n1 = 0, n2 = 1;
  for (; i <= n; i++) {
    t = n2 + n1;
    n1 = n2;
    n2 = i < 2 ? 1 : t;
  }
  return t;
}

var ns = process.argv.slice(2);

var s1 = Date.now();

ns.forEach(function (n, i) {
  console.log(i + '. ', n, ': ', fibonacci(n));
});

var s2 = Date.now();

var t1 = s2 - s1;

ns.forEach(function (n, i) {
  console.log(i + '. ', n, ': ', fibonacci3(n));
});

var s3 = Date.now();

var t2 = s3 - s2;

ns.forEach(function (n, i) {
  console.log(i + '. ', n, ': ', fibonacci2(n));
});

var s4 = Date.now();

var t3 = s4 - s3;

console.log(t1 + 'ms', t2 + 'ms', t3 + 'ms');