<button id="btn">Click or Enter</button>

const btn = document.querySelector("#btn");

buttonEvent = (event) => {
  console.log(event);
  if(event.type == 'keydown' && event.keyCode === 13) {
    alert("enter");
  }
  else if(event.type == "click") {
    alert("click");
  }
};

btn.addEventListener("click", buttonEvent);
//btn.addEventListener("keydown", buttonEvent);