javascriptintermediate

JavaScript DOM Manipulation

DOM manipulation and event handling

7 questions

By EZ4Code TeamLast updated: 2026-08-01

1. What is the method to get an element by id?

document.getElementById('id')

document.getById('id')

document.querySelector('#id') only for class

document.find('id')

Explanation: getElementById gets a single element by its id; querySelector('#id') also works, but the former is more direct and efficient.

2. What does it mean when the third parameter (boolean) of addEventListener is true?

Triggers the event during the capture phase

Triggers the event during the bubbling phase

Triggers only once

Prevents default behavior

Explanation: A third parameter of true means triggering during the capture phase; false (default) means triggering during the bubbling phase.

3. What mechanism does event delegation mainly utilize?

Event bubbling, handling child element events uniformly on the parent element

Event capture

Event loop

Promise

Explanation: Event delegation leverages event bubbling to bind child element events uniformly to the parent element, reducing the number of bindings and supporting dynamic child elements.

4. What is the method to create a new element node?

document.createElement('div')

document.newElement('div')

document.create('div')

document.makeNode('div')

Explanation: createElement(tagName) creates an element node with the specified tag name, which needs to be inserted into the document with appendChild etc.

5. Which method can prevent the default behavior of an event?

event.preventDefault()

event.stopPropagation()

event.stop()

event.cancel()

Explanation: preventDefault() prevents default behavior (such as link navigation, form submission); stopPropagation() stops event bubbling.

6. What does the toggle method of classList do?

Toggles a class name: removes if present, adds if absent

Permanently adds a class name

Permanently removes a class name

Queries whether a class name exists

Explanation: classList.toggle(cls) toggles a class name on an element: if present, removes it and returns false; if absent, adds it and returns true.