ES6 rewindable iterators

rewindable-it.js

function range(n) {
  var i = 0
  
  return { next: step, rewind: rewind }

  function step() {
    return i++ < n? { value: i } : { done: '110%' }
  }

  function rewind() { i = 0 }
}

var ten = range(5)

for (var n of ten) console.log(n)
for (var n of ten) console.log('not called')

ten.rewind()

console.log('erase and rewind')
for (var n of ten) console.log(n) // Works again

$ node --harmony rewindable-it.js 
1
2
3
4
5
erase and rewind
1
2
3
4
5