Double spread problem - getting rid of Object.assign()

Question

Here is my reducer body code fragment:

const newState = {
    ...state,
    programs: {
        ...state.programs,
        ...Object.assign(
            {},
            ...action.payload.map(
                (channelName) =>
                    ({
                        [channelName]: {
                            ...state.programs[channelName],
                            selected: true
                        }
                    })
            )
        )
    }            
}
return newState

Is there any chance to get rid of Object.assign in this case?

The classical advice to change Object.assign({}, a) to { ...a } does not work in this case, because here we already have ...action.payload.map, so it would result in ... { ...a } which makes spread to produce array-like keys of 0,1,2...

Is there any elegant way to transform my code correctly?

Answer 1

Another option to use Object.fromEntries:

const action = {
  payload: ['discoveryChannel']
}

const state = {
  programs: {
    cartoonNetwork: {
      description: '',
      when: new Date()
    },
    discoveryChannel: {
      description: '',
      when: new Date()
    }
  }
}

const newState = {
  ...state,
  programs: {
    ...state.programs,
    ...Object.fromEntries(
         action.payload.map(
           channelName => ([
             channelName, {...state.programs[channelName], selected: true}
           ])
         )
       )
  }
}
console.log(newState);