How to implement fifo queue with Reactjs&Redux

Question

Hello i need some help about react-redux because im still learning, lets say im trying to make simple Queue Management, and i have this reducer:

const initialState = {
    currentQueue = {},
    queues=[],
    loading: false
}

and the data would be like:

currentQueue: 
{{'id_queue': '1', 'queue_no': 'A001', 'status': 0}}

queues:
[0:{'id_queue': 1, 'queue_no': 'A001', 'status': 0 },
 1:{'id_queue': 2, 'queue_no': 'A002', 'status': 0 }]

How to get single object from queues array to currentQueue ? like next queue, i only know to get object by id (like people profile). so i need to render the queue array list one-by-one to show current queue number, or should i just manipulate the mysql query limit by 1 ?.

Please give enlighten me to implement proper queue in react-redux with mysql if there any better way, thank you. Because im already tried to search some queue implementation with react-redux but no luck.

Answer 1

javascript arrays can act like a fifo queue.

const fifo = [];
fifo.push(1)
fifo.push(2)
console.log(fifo.push(3)) // undefined
console.log(fifo) // [1, 2, 3]
const val = fifo.shift()
console.log(val, fifo) // 1, [2, 3]

However push, pop, unshift and shift all mutate the array. Here is an immutable way.

function immutablePush(arr, newEntry){
  return [ ...arr, newEntry ]      
}

function immutableShift(arr){
  return arr.slice(1)     
}

const fifo = [];
immutablePush(fifo, 1) // returns [1]
immutablePush(fifo, 2) // [1, 2]
immutablePush(fifo, 3) // [1, 2, 3] 
const val = fifo[0] // 1
immutalbeShift(fifo) // returns [2, 3]

If you want to lookup data like you do in a object, you will need to normalize data.

In most cases you can simply use findIndex

const findByIdQueue(array, id) => {
  const i = array.findIndex(item => item.id_queue === id);
  // if i = -1 (not found) return undefined else return found item
  return ~i ? undefined : array[i];
}

In react redux, we want to separate our access and update code. We access with selectors:

const selectFirstItem = state => {
  // access state.fifo but set fifo to [] if state or state.fifo are undefined
  const { fifo = [] } = state || {};
  // return first array item or undefined if there is an empty list
  return fifo[0]; 
}
const selectItemById = (state, ownProp) => {
  const { fifo = [] } = state || {};
  const { id } = ownProp || {};
  return findByIdQueue(fifo, id);
}
const mapStateToProps = (state, ownProp) => ({
  firstItem = selectFirstItem(state);
  itemById = select(state, ownProp)  // expect parent of MyCoolControl to pass in prop id
// <MyCoolControl id={24} />
})

export default connect(mapStateToProps)(MyCoolControl)

We update with actions:

const addItem = item => ({type: 'ADD_ITEM', item})
const removeFirstItem = () => ({type: 'REMOVE_FIRST_ITEM'})

const fifoReducer = (prev = defaultValue, action = {}) => {
  const { type, item} = action;
  switch (type) {
    case "ADD_ITEM":
      return [...prev, item];
    case "REMOVE_FIRST_ITEM":
      return prev.slice(1);
    default: {
      return prev;
    }
  }
};