Examples of using ES6 generators

counter.js

function* counter() {
  var n = 0;
  while (true) {
    yield n++;
  }
}

for (var number of counter()) {
  console.log('counter is at', number);
}

fibonacci.js

function* fibonacci() {
  var i = 0, n = 1, keepGoing = true
  while (keepGoing) {
    if (i === i/0) {
      keepGoing = false
      continue
    }
    yield i
    var t = i
    i = n
    n += t
  }
}

// Shortcut for firing .next() to get each yielded value
for (var i of fibonacci()) {
  console.log(i)
}

// You could also do it like this to get the first 50 in the sequence
// var fib = fibonacci()
// for (var i = 0; i < 50; i++) {
//   val = fib.next().value
//   console.log(val)
// }