Question

48

Cannot convert undefined or null to object redux

rated 0 times [ 52] [ 4] / answers: 1 / hits: 15809 / 7 Years ago, mon, may 29, 2017, 12:00:00

I'm using Redux to make a simple store and unfortunately it's throwing this error:

 Cannot convert undefined or null to object

The browser points to the line of importing Redux

import * as redux from redux

I've also tried to import it this way but it gave the same error
import { createStore } from redux

this the code :

import * as redux from redux



let reducer = (state ={}, action) =>{

    switch(action.type) {

        case ADD_POLL:

            return {

                polls: [

                    ...state.polls,

                    action.poll

                ]

            }

        default:

            return state

    }

}



let store = redux.createStore(reducer)



store.subscribe(()=>{

    let currentState = store.getState()

    console.log(currentState)

})



store.dispatch({

    type: ADD_POLL,

    poll: {

        id: 1,

        title: What's  your fav Color,

        votes: 230

    }

})

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dewayneh

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3 Years ago

answered 7 Years ago parker · Accepted Answer

That error is thrown as in your reducer you are trying to spread a non existent property on the state object

...state.polls,

To be able to do so you have to define the shape of your initial state as

const initialState = {

    polls: [],

};

Full working code of your example

import * as redux from redux



const initialState = {

    polls: [],

};



const reducer = (state = initialState, action) =>{

    switch(action.type) {

        case ADD_POLL:

            return {

                polls: [

                    ...state.polls,

                    action.poll

                ]

            }

        default:

            return state

    }

}



const store = redux.createStore(reducer)



store.subscribe(()=>{

    let currentState = store.getState()

    console.log(currentState)

})



store.dispatch({

    type: ADD_POLL,

    poll: {

        id: 1,

        title: What's  your fav Color,

        votes: 230

    }

})