HTML

dom button

<button name="favorite">
  <svg aria-hidden="true" viewBox="0 0 10 10"><path d="M7 9L5 8 3 9V6L1 4h3l1-3 1 3h3L7 6z"/></svg>
  Add to favorites
</button>

button DOM

const btn = document.querySelector("button");
const txt = document.querySelector("p");

btn.addEventListener("click", updateBtn);

function updateBtn() {
  if (btn.textContent === "Start machine") {
    btn.textContent = "Stop machine";
    txt.textContent = "The machine has started!";
  } else {
    btn.textContent = "Start machine";
    txt.textContent = "The machine is stopped.";
  }
}