CODEWITHSUNDEEP
reactjsredux
Anton
Anton

Reputation: 2138

Redux - What is immutable state change for reducer?

Two functions to change reducer state:

function1 (state, newValue) {
    const newValue1 = newValue + 1;
    const newValue2 = newValue * 7;
    return {...state, newValue2}
}

function2 (state, newValue) {
    let newValue1 = newValue + 1;
    newValue1 = newValue1 * 7;
    return {...state, newValue1}
}

Which one is correct? Does only state has to be immutable or any variable?

Upvotes: 0

Views: 118

Answers (2)

Radosław Miernik
Radosław Miernik

Reputation: 4094

Both are correct. As you've said, only the state has to be immutable. In your case, simply don't mutate the state variable in any way.

Upvotes: 1

I'm Joe Too
I'm Joe Too

Reputation: 5840

The idea behind an immutable state object is just that you don't change state directly. So doing this would be wrong:

let state = {...}
function changeState(newValue) {
  state.newValue = newValue
}

I don't know the rest of your code to say it's right or wrong, but in the examples you provided, you are not mutating state - you're returning a new object that takes everything from the existing state as-is (destructuring state with ...state) and adding or overriding newValue in the newly returned object.

As to whether or not it's wrong to change newValue (or other variables), again both of your instances are fine. It's perfectly find to use, change, and run logic in your reducers to ultimately come up with a new object (or whatever) for the updated state.

Upvotes: 0

Related Questions