gistfile1.js

function* foo() {
  // Parallel calls with no helper lib
  var paths = ['A.js', 'B.js']
  var group = []
  for (path in paths) {
    group.push(fs.readFile(path))
  }
  var files = yield group

  // Serial calls
  var filesTwo = yield fs.readFile(files[0])
}

run(function*() {
  // try/catch works across ticks
  try {
    var value = yield* foo(argOne)
  } catch(e) { … }
})