JavaScript & the DOM

the intro

JavaScript makes pages interactive. The browser exposes the page as the DOM — a live tree of objects — and JavaScript can find nodes, listen for events, and change anything. Master querySelector, addEventListener, and events like click and input, and you can build real behavior.

the sample

listen, react, update

const btn = document.querySelector("#go")
btn.addEventListener("click", () => {
  document.querySelector("#out")
    .textContent = "clicked!"
})

the docs