For example, current state is:

    {
     data: [
      {id: 1, number: 100},
      {id: 2, number: 200},
      {id: 3, number: 300}
     ]
    }

Action is:

   const action = (id, number) => {
    return {id: id, number: number}
   }

How to implement reducer that it meets the following requirements:

1. If the state (array of objects) doesn't have an object with the same id as an ining object - push the ining object to the state;
2. If the state has an object with the same id as an ining object - update this object in state with number field value of an ining object.

CASE 1:

//ining object
{id: 4, number: 400}

//result
    {
     data: [
      {id: 1, number: 100},
      {id: 2, number: 200},
      {id: 3, number: 300},
      {id: 4, number: 400}
     ]
    }

CASE 2:

//another ining object
{id: 2, number: 250}

//result
    {
     data: [
      {id: 1, number: 100},
      {id: 2, number: 250},
      {id: 3, number: 300},
      {id: 4, number: 400}
     ]
    }

Maybe it has a simple solution, but I can't find the right approach to solving this problem:) Also I would like to know what is the best practice in cases like this.

Thank you in advance

For example, current state is:

    {
     data: [
      {id: 1, number: 100},
      {id: 2, number: 200},
      {id: 3, number: 300}
     ]
    }

Action is:

   const action = (id, number) => {
    return {id: id, number: number}
   }

How to implement reducer that it meets the following requirements:

1. If the state (array of objects) doesn't have an object with the same id as an ining object - push the ining object to the state;
2. If the state has an object with the same id as an ining object - update this object in state with number field value of an ining object.

CASE 1:

//ining object
{id: 4, number: 400}

//result
    {
     data: [
      {id: 1, number: 100},
      {id: 2, number: 200},
      {id: 3, number: 300},
      {id: 4, number: 400}
     ]
    }

CASE 2:

//another ining object
{id: 2, number: 250}

//result
    {
     data: [
      {id: 1, number: 100},
      {id: 2, number: 250},
      {id: 3, number: 300},
      {id: 4, number: 400}
     ]
    }

Maybe it has a simple solution, but I can't find the right approach to solving this problem:) Also I would like to know what is the best practice in cases like this.

Thank you in advance

• javascript
• reactjs
• redux
• react-redux

• Add logic to update or insert in your reducer. – Berk Kurkcuoglu Commented Oct 13, 2020 at 21:27
• Another approach that might be possible is to swap out the array you store in redux for a Record that uses the id of each object as a key. This means that checking an id exists is as simple as !!data[id] and assigning to it data[id].number = 500;. Depending on how plex the reducer is an what other actions it requires this could possibly be an option. The redux docs have more information – Jacob Smit Commented Oct 13, 2020 at 21:37

2 Answers 2

I changed your action to use the payload property, but if you want you can remove it. (It's more proper to have it)

const reducer = (state, action) => {
  switch(action.type) {
    case 'UPDATE_OR_INSERT':
      return {
        data: [
          ...state.data.filter(x => x.id !== action.payload.id),
          action.payload,
        ]
      }
     default:
  }
  return state;
}

console.log(
  reducer({
    data: [
      {id: 1, number: 100},
      {id: 2, number: 200},
      {id: 3, number: 300},
      {id: 4, number: 400}
     ]
    }, { type: 'UPDATE_OR_INSERT', payload: {id: 2, number: 250}}));

How do you think of this solution?

const testState = {
    data: []
}

export default (state = testState, action) => {
    switch(action.type){
        case "SET_DATA":
            return [
                ...state.data.filter(d => d.id !== action.payload.id),
                action.payload,
            ];
        default:
            return state;
    }
};