js generators sample

generator.js

// based on redux-saga api
const select = (fn) => ( { type: 'select', fn: fn } )
const put = (action) => ( { type: 'put', action: action } )
const call = (fn, ...args) => ( { type: 'call', fn: fn, args: args } )

function callSaga(iterator) {
  let ret;

  ret = iterator.next();
  while(!ret.done) {
    var nextVal = callFn(ret.value);
    ret = iterator.next(nextVal);
  }

}

function callFn(fnObj) {
  const type = fnObj.type;
  if(type === 'select') {
    return fnObj.fn(getState());
  } else if (type === 'put'){
    return dispatch(fnObj.action);
  } else if (type === 'call') {
    return fnObj.fn(...fnObj.args);
  }
}

function getState() {
  return {
    a: 1,
    b: 2
  }
}

function dispatch(action) {
  console.log(action)
}


/// saga
const fromState = v => state => state[v]
const getRandom = () => Math.floor(Math.random() * 10);
function* saga() {
  const a = yield select(fromState('a'));
  const b = yield select(fromState('b'));

  yield put({ type: 'UPDATE_A', value: a+b });

  const newB = yield call(getRandom);

  yield put({ type: 'UPDATE_B', value: newB })

  yield call(console.log, a+b, newB);
}

i=saga();
callSaga(i);