Recall Previous States with XState History States Nodes

Generally speaking, state machines do not and should not have a sense of time. They are intended to be pure functions that receive a state and event and return the next state. Pure functions by design have no sense of history.

Yet, it is occasionally useful to return to a previous state. How is this accomplished? With history state nodes. Each state object returned by XState contains a special property that points to the previous state. When a history state node is defined and is the target of a transition, the machine returns to this previously stored state.

We can create a history node by defining the type as history, and setting the history property to either shallow (the default) or deep.