React updating single object of an array of objects - map vs entire array

Question

I have a component with an array of objects in local state:

    const [myState, setState] = useState<SomeObjectType[]>([]);

I can update a single object in that array by making a copy of the entire array and then update the property of the single object I wish to update:

OPTION 1


    const state = [...myState];
    state[id].description = description;
    setState(state);

Or I can use map:

OPTION 2


  const newState = talkingPoints.map(el => {
      // 👇️ if id equals, update description property
      if (el.id === id) {
        return {...el, description};
      }

      // 👇️ otherwise return as is
      return el;
    });

    setData(newState);

Or can I do this (since I am 100% certain the id exists in the array)?

OPTION 3

  const handleUpdate = () => {
    setState(prevState => ({
      ...prevState,
      prevState[id].description = description
    }))
  }

For cases where I am not 100% certain I can use map and find it:

OPTION 4

  const handleUpdate = () => {
    setState(prevState => ({
      myState: prevState.myState.map(el => el.id === id ? { ...el, description } : el)
    }))
  }

What is recommended/best practice? Is Option 1 (fully array copy) faster than using map?

Enfield Li · Accepted Answer · 2022-05-16 17:19:59Z

7

Option 3 and opntion 4 are incorrect, the prevState/myState is an array and you are returning an object, this will surely cause error in typescript. As to option 1 and 2, they only differ between declaritive and imperitive way of programming. And declaritive programming makes more readable code.

On option 1:

const newState = [...myState];
newState[index].description = "new desc"; 
// Access index position as opposed to id
// since the item's position may not align with it's id
setState(newState );

On option 2 with map function, it can be written as follows:

setState(myState.map(item => item.id === id ? {...item, item.description: "new desc"} : item))

In conclusion, use map/filter is more preferable to update array.

Here's sandbox to compare option 1 and 2

edited May 16, 2022 at 17:19

answered May 16, 2022 at 16:21

Enfield Li

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