test.ts

interface State {
    DoThing(): void;
}

class StandState implements State {
    DoThing() {
        console.log("Doing stand thing");
    }
}

class JabState implements State {
    DoThing() {
        console.log("Doing jab thing");
    }
}

abstract class Fighter  {
    protected StandState = StandState;
    protected JabState = JabState;

    private currentState: State;

    DoState() {
        if (this.currentState)
            this.currentState.DoThing();
    }

    SetState() {
        this.currentState = new this.StandState();
    }
}

class SpecificStandState implements State {
    DoThing() {
        console.log("Doing specific stand thing");
    }
}

class SpecificFighter extends Fighter {
    protected StandState = SpecificStandState; 
}

let fighter = new SpecificFighter();

fighter.SetState();
fighter.DoState();