state-machine.ts

interface IStateMachine<TState,TEvent, TPayload = {}> {
    getState():TState;
    dispatch(event: TEvent, payload?: TPayload): IStateMachine<TState,TEvent, TPayload>;
}

type MyEvent = 'start' | 'move' | 'stop';
type MyState = {speed: number, isHealthy: boolean};

class MyStateMachine implements IStateMachine<MyState, MyEvent> {
    constructor(private _state: MyState, private readonly _reaction: Record<MyEvent,(state:MyState)=> MyState>){}

    getState(): MyState {
        return this._state;
    }

    dispatch(event: MyEvent) {
        const reaction = this._reaction[event];
        this._state = reaction(this._state);
        console.log(this._state);
        return this;
    }
}