CODEWITHSUNDEEP
javascriptreactjsreduxreact-reduxdynamic-arrays
Nikul Patel
Nikul Patel

Reputation: 33

modifiying nested redux state without mutating

Am i Mutating redux state with this function ? 

function addDefinition(object, payload) {
    var newObject = Object.assign({}, object);
    if(!newObject[payload.guid]){
    newObject[payload.guid] = [];
    }
    newObject[payload.guid].push(payload);
    return newObject;
}

I want to create structure to hold data related to different part of application.

Upvotes: 0

Views: 56

Answers (2)

Galupuf
Galupuf

Reputation: 2957

Yes. See markerikson's answer. Keep in mind you could avoid this with the spread operator.

const INITIAL_STATE = {
  guid: []
}

function addDefinition(state = INITIAL_STATE, payload) {

  return {...state, guid: [...state.guid, payload]};

}

In addition you could avoid the if statement with initial state.

Upvotes: 0

markerikson
markerikson

Reputation: 67539

Yes, that .push() statement is mutating in the later calls. In the first call, the array is newly created, so it doesn't qualify as a mutation. In a later call, you've created a new object but copied the existing array reference, so .push() mutates the existing array.

Upvotes: 1

Related Questions