Learning Redux

A new kind of history

However, there is a different way we can store the history, that is, by tracking the past and future states in arrays and storing the present state beside them:

{  past: [...],  present: ...,  future: [...]}

A nice bonus of using this history structure is being able to simply access the present state through state.present instead of having to select it from the array by index using, for example, state.history[state.currentState]

If we try the same scenario with this kind of history, we will have the following state after three increment actions:

{  past: [0, 1, 2],  present: 3,  future: []}

Each undo action pushes the present state to the beginning of the future array and removes the last element from the past array, setting ...