index.js

let homeScoreBtnOne = document.getElementById("home-score-btn-1");
let homeScoreBtnTwo = document.getElementById("home-score-btn-2");
let homeScoreBtnThree = document.getElementById("home-score-btn-3");
let homeScoreEl = document.getElementById("home-score");
let homeScore = 0;

function increaseHomeScoreOne() {
  homeScore += 1;
  homeScoreEl.textContent = homeScore;
}
function increaseHomeScoreTwo() {
  homeScore += 2;
  homeScoreEl.textContent = homeScore;
}
function increaseHomeScoreThree() {
  homeScore += 3;
  homeScoreEl.textContent = homeScore;
}

let guestScoreBtnOne = document.getElementById("guest-score-btn-1");
let guestScoreBtnTwo = document.getElementById("guest-score-btn-2");
let guestScoreBtnThree = document.getElementById("guest-score-btn-3");
let guestScoreEl = document.getElementById("guest-score");
let guestScore = 0;

function increaseGuestScoreOne() {
  guestScore += 1;
  guestScoreEl.textContent = guestScore;
}
function increaseGuestScoreTwo() {
  guestScore += 2;
  guestScoreEl.textContent = guestScore;
}
function increaseGuestScoreThree() {
  guestScore += 3;
  guestScoreEl.textContent = guestScore;
}

let bothScoreBtnZero = document.getElementById("reset-btn");
function resetScoreZero() {
  guestScore = 0;
  guestScoreEl.textContent = 0;
  homeScore = 0;
  homeScoreEl.textContent = 0;
}