Learning Redux

Handling the undo action

On an undo action, we want to do the following steps:

• Remove the last element from the past
• Insert the current present state at the beginning of the future
• Set the present to the element we removed from the past in the first step

Replace the return state // TODO line following case actionTypes.UNDO, by doing the following:

1. First, we check whether there are elements in the past array. If not, we simply return the current state:

        if (past.length <= 0) return state

2. Next, we store the last element from the past, because we will need it in the last step:

        const previous = past[past.length - 1]

3. Then, we create a new array from the past array, with the last element excluded:

 const newPast = past.slice(0, past.length ...