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dom-manipulation

DOM manipulation

Last reviewed May 28, 2026 Content v20260528
Track mode
client_javascript
Means
In-browser JS
Reading
~1 min
Level
intermediate

This lesson

This lesson teaches DOM manipulation—the ideas, syntax, and habits you need before moving on in JavaScript.

DOM skills connect markup from the HTML track to behavior users actually see.

You will apply DOM manipulation in contexts like: Interactive pages, SPAs, browser extensions, and client-side validation.

Run JavaScript in the in-browser sandbox, use the terminal output panel, and verify with MCQs.

When the previous lesson's MCQs feel easy and you can explain DOM manipulation in your own words.

Change structure and presentation: textContent, innerHTML (careful with XSS), classList, and createElement.

Safe text

Prefer textContent for user-visible strings—innerHTML parses HTML and can execute scripts if data is untrusted. See XSS lesson.

classList

el.classList.add('active') — toggles pair with CSS from the CSS track.

Important interview questions and answers

  1. Q: textContent vs innerHTML?
    A: textContent escapes; innerHTML interprets tags.
  2. Q: createElement workflow?
    A: Create node, set properties, append to parent.

Self-check

  1. Why avoid innerHTML with user input?
  2. What does classList.toggle do?

Pitfall: innerHTML with user input enables XSS—use textContent.

Interview prep

textContent vs innerHTML?

textContent is safe for plain text; innerHTML parses HTML.

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Not saved yet.

Playground

Runs in your browser in a sandboxed frame. Backend runners appear when this track’s profile allows them.

Check yourself

Multiple choice — immediate feedback.

Discussion

Past discussion is visible to everyone. Only logged-in users can post comments and replies.

Starter discussion topics

  • What would you log to verify this behavior?
  • What breaks if you run this before the DOM is ready?

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