Redux shopping cart example - reactjs

Question

I'am trying to understand the example named "shopping cart" giving for redux :
https://github.com/reactjs/redux/tree/master/examples/shopping-cart
In this example you can add elements to your list of items, I tried to implement the function of remove a list of items :
But in the reducers folder there is an addedIds() function, I added a case to remove the element of the list but I don't know how to implement that, here is the function : the reste of my code is working fine I just don't know how to delete the product id from the array of addedIds.
const initialState = {
addedIds: [],
quantityById: {}
};
function addedIds(state = initialState.addedIds, action) {
switch (action.type) {
case ADD_TO_CART:
console.log("added ADD");
if (state.indexOf(action.productId) !== -1) {
return state
}
return [ ...state, action.productId ];
case REMOVE_TO_CART:
console.log("removed ADD");
// here is my problem
default:
return state
}
}
I assumed I need to do something like here :
Is this the correct way to delete an item using redux?
but I don't know how
Can you help me please ?

Answer 1

You can delete some element from array just filtering it out:
// ... skipped other cases from the switch
case REMOVE_TO_CART:
return state.filter(productId => action.productId !=== productId)
Approach with .filter() function looks very short and produces a new array instance as it required by redux.

Answer 2

For those who have a similar problem here is the solution :
const initialState = {
addedIds: [],
quantityById: {}
};
function addedIds(state = initialState.addedIds, action) {
switch (action.type) {
case ADD_TO_CART:
console.log("added ADD");
if (state.indexOf(action.productId) !== -1) {
return state
}
return [ ...state, action.productId ];
case REMOVE_TO_CART:
console.log("removed ADD");
return [ ...state.slice(0,state.indexOf(action.productId),
...state.slice(state.indexOf(action.productId)+1))
];
default:
return state
}
}
thanks to Josh Deeden who found this vidéo :
https://egghead.io/lessons/javascript-redux-avoiding-array-mutations-with-concat-slice-and-spread