Fibonacci with TCO https://google.github.io/traceur-compiler/demo/repl.html

fib.js

// Options: --proper-tail-calls 

"use strict";

var cache = {};
function fib(n) {
  return fib_(n, _ => _);
}
function fib_(n, callback) {
  if (n === 0) return callback(0);
  if (n === 1) return callback(1);
  if (cache[n]) return callback(cache[n]);
  return fib_(n - 1, p1 => fib_(n - 2, p2 => callback(cache[n] = p1 + p2)));
}

console.log(fib(10000));