const counter = (
  <div className="container">
    <div className="plus">+</div>
    <div className="num">0</div>
    <div className="minus">-</div>
  </div>
);

ReactDOM.render(counter, document.querySelector("#root"));

const plus = document.querySelector(".plus");
let num = document.querySelector(".num");
const minus = document.querySelector(".minus");

const plusNum = () => (num.innerHTML = Number(num.textContent) + 1);

const minusNum = () => {
  if (Number(num.textContent) > 0) {
    num.innerHTML = Number(num.textContent) - 1;
  }
};

plus.addEventListener("click", plusNum);
minus.addEventListener("click", minusNum);