generatorz

index.js

function *write(){
  console.log('writing');
  var num = yield 1;
  console.log('num x num =', num * num);
}

function *blah () {
  console.log('starting blah');
  yield* write();
  console.log('ending blah');
}

var it = blah();
it.next(); 
it.next(9);