Users generate events (click, input, keydown). Register listeners with addEventListener—prefer over inline HTML handlers.
Listener pattern
btn.addEventListener('click', (e) => {
e.preventDefault();
// handle
});Event object
preventDefault stops default browser action (form submit, link navigation). stopPropagation limits bubbling.
Important interview questions and answers
- Q: Bubbling?
A: Event travels from target up ancestors—delegation exploits this. - Q: removeEventListener?
A: Need same function reference—named functions help.
Self-check
- What does preventDefault do on a form?
- What is event bubbling?
Tip: Re-run the playground code for events-listeners and tweak one line before the MCQs.
Interview prep
- preventDefault?
Blocks default browser action for the event.