generators-run.js

function run (generator) {
  var data = null, yielded = false
  var iterator = generator(function () {
    data = arguments
    check()
  })
  yielded = !!(iterator.next())
  check()
  function check () {
    while (data && yielded) {
      var err = data[0], item = data[1]
      data = null
      yielded = false
      if (err) return iterator.throw(err)
      yielded = !!(iterator.next(item))
    }
  }
}