CODE EXAMPLE FOR JAVASCRIPT

reducer function redux

{/**The logic inside reducer functions typically follows the same series of steps:

Check to see if the reducer cares about this action
If so, make a copy of the state, update the copy with new values, and return it
Otherwise, return the existing state unchanged
Here's a small example of a reducer, showing the steps that each reducer should follow:
*/}

const initialState = { value: 0 }

function counterReducer(state = initialState, action) {
  // Check to see if the reducer cares about this action
  if (action.type === 'counter/incremented') {
    // If so, make a copy of `state`
    return {
      ...state,
      // and update the copy with the new value
      value: state.value + 1
    }
  }
  // otherwise return the existing state unchanged
  return state
}

//Reducers can use any kind of logic inside to decide what the new state should be: if/else, switch, loops, and so on.