Selecting Elements — JS Technical Interview Questions & Answers

getElementById, querySelector, querySelectorAll.

Selecting Elements

  • Selecting Elements (js dom) is a JS topic. In plain words you use it for click Save in a form page. Don’t start with a slogan — start with that picture.
  • Smallest example: addEventListener('click', …). Type it, run it, and say what you see. If you can do that from memory, you know Selecting Elements (js dom).
  • From the example next to this theory: getElementById, querySelector, querySelectorAll.
  • Trap: listener on a node that gets replaced. Fix that before you talk about advanced JS.
  • Viva: what is Selecting Elements (js dom)? Then show addEventListener('click', …). Then name the trap.

Technical Interview Tip: What is Selecting Elements (js dom)? Show this: addEventListener('click', …). Trap: listener on a node that gets replaced.

Code Examples for Selecting Elements

Selecting Elements — working example

// Browser:
// const btn = document.querySelector("#save");
// btn?.addEventListener("click", (e) => {
//   e.preventDefault();
//   btn.classList.toggle("busy");
// });

// Runnable stand-in (no DOM in Node/Piston):
const menu = { className: "menu" };
function toggleOpen() {
  const parts = new Set(menu.className.split(/\s+/).filter(Boolean));
  if (parts.has("open")) parts.delete("open");
  else parts.add("open");
  menu.className = [...parts].join(" ");
}
toggleOpen();
console.log(menu.className);

Selecting Elements — in the browser, select nodes then attach listeners. Here we simulate classList toggling.

How to Explain Selecting Elements to an Interviewer

What is Selecting Elements (js dom)?

Used for click Save a form page Not just the heading

Give one small example of Selecting Elements (js dom).

addEventListener('click', …) getElementById, querySelector, querySelectorAll

What mistake do beginners make with Selecting Elements (js dom)?

listener on a node that gets replaced Show the fix

Where do you use Selecting Elements (js dom)?

a form page click Save