Quiz

JavaScript DOM Quiz

8 questions about working with a page through JavaScript: selecting elements, events, and changing content.

questions

~4 min

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Question 1 of 8

Which method finds the first element matching a CSS selector?

getElementById()✓✗ querySelector()✓✗ getElementsByClass()✓✗ findElement()✓✗

Question 2 of 8

What does document.querySelectorAll(".item") return?

A single element✓✗ An array of strings✓✗ A NodeList of all matching elements✓✗ undefined if there are none✓✗

Question 3 of 8

How do you attach a click handler to a button?

btn.click = function(){}✓✗ btn.addEventListener("click", fn)✓✗ btn.event("click", fn)✓✗ btn.on("click", fn)✓✗

Question 4 of 8

What's the difference between innerHTML and textContent?

Nothing, they're the same✓✗ innerHTML sets HTML markup, textContent sets plain text only✓✗ textContent sets HTML, and innerHTML sets plain text only✓✗ innerHTML is read-only✓✗

Question 5 of 8

Which event fires when a select or input value changes and loses focus?

onclick✓✗ onchange✓✗ onsubmit✓✗ onload✓✗

Question 6 of 8

How do you stop a form's default submit behavior?

event.stop()✓✗ event.preventDefault()✓✗ form.cancel()✓✗ return false always works✓✗

Question 7 of 8

How do you add a CSS class to an element with JavaScript?

el.class.add("active")✓✗ el.classList.add("active")✓✗ el.addClass("active")✓✗ el.style.class = "active"✓✗

Question 8 of 8

What is event bubbling?

An event that only happens on one element✓✗ An event that travels upward from the child element to its parents✓✗ A mechanism that automatically blocks events✓✗ An outdated mechanism no longer used✓✗

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