Pages that listen
Pages come alive when they react: a click, a key press, a mouse hovering. Each of those is an event, and JavaScript can listen for them.
addEventListener
const button = document.querySelector("#like");
const count = document.querySelector("#count");
let likes = 0;
button.addEventListener("click", () => {
likes++;
count.textContent = likes;
});A doorbell: addEventListener is like wiring a doorbell: "when someone presses this, play this tune". The tune doesn't play when you wire it — only when it's pressed.