JS Function won't generate necessary buttons

Question

I am currently making a budget version of UNO using Java and JavaScript and I am running all of it on a GlassFish Server.

I made a function to generate the starting hand of 7 cards for each player, yet it doesn't behave like I want it to. (I am kind of an amateur in programming)

Here is my function for generating the cards:

function getStartingCards(){

    fetch('./api/cards')
        .then(response => response.json() )
        .then( data => {

            _cards = data;
            let html = "";

            data.forEach(d => html += `<tr><td><button class="card1">test</button></td></tr>`);
            document.getElementById("table1").innerHTML = html;

            console.log("test");

        })

}

That was my front-end, which is supposed to generate the cards itself with some things it receives from the back-end:

@Path("/cards")
public class CardsResource {

    @Context
    ContainerRequestContext c;

    @GET
    public List<Hand> getCard(){

        return HandDatabase.getInstance().getCardList();

    }

   @POST
    public Response addCard(@QueryParam("id") int id){

        try{

            Card card = Deck.getInstance().dealCard();

            String hand = (String)c.getProperty("user");

            HandDatabase.getInstance().getHandById(hand).addCard(card);

            return Response.ok(Deck.getInstance().dealCard()).build();

        }catch (Exception e){

            return Response.status(Response.Status.NOT_FOUND).build();

        }

    }

}