CSS vs JS Transitions
Choose between CSS keyframe transitions and JavaScript tick functions.
CSS vs JS Transitions is a free Sveltejs Academy lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Sveltejs Academy learning path, and your progress syncs across the web and the CoddyKit app. The Sveltejs Academy course includes 4 lessons in total.
Two Modes
Custom transitions return either a css function (GPU) or a tick function (JS-driven per frame).
When to Use CSS
For transform, opacity, color — anything CSS can animate. CSS runs on the compositor for 60fps.
When to Use Tick
For text changes, canvas pixels, or other non-CSS properties.
Tick Cost
Tick runs on every animation frame in JavaScript. More expensive than CSS.
Hybrid Approach
Some transitions can use CSS for visuals and tick for occasional non-CSS updates.
Cross-Browser
CSS animations are universally supported; tick is always available since it is JS.
Accessibility
Both respect prefers-reduced-motion if you check it inside your transition.
Profiling
Use the Performance tab to compare CSS vs tick implementations.
Fallback Pattern
If CSS cannot achieve the effect, gracefully fall back to tick.
Combining
Multiple elements with different transitions can mix CSS and tick in the same view.
Best Practice
Default to CSS. Reach for tick only when CSS truly cannot express the animation.
Quick Check
When should you prefer the css function in a transition?
Recap
Choose css for GPU-accelerated transitions; reserve tick for non-CSS animations like text or canvas changes.
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Frequently Asked Questions
Is the “CSS vs JS Transitions” lesson free?
Yes — the full text of “CSS vs JS Transitions” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Sveltejs Academy course, upgrade to CoddyKit PRO. The Sveltejs Academy course includes 4 lessons in total.
What will I learn in “CSS vs JS Transitions”?
Choose between CSS keyframe transitions and JavaScript tick functions. You practise Sveltejs Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Sveltejs Academy?
No prior experience is required. Sveltejs Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.
How long does the “CSS vs JS Transitions” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Sveltejs Academy lesson?
Yes. Every Sveltejs Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Writing a Custom Transition Function
- Transition Parameters: node duration delay
- Creating a morphing Transition
- CSS vs JS Transitions