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JavaScript Academy · Lesson

Scroll-Triggered Animations

Animate elements as they enter view.

Animating on Scroll

A popular effect is fading or sliding elements into view as the user scrolls to them. Intersection Observer makes this clean: add a CSS class when an element enters the viewport, and let CSS handle the animation.

The CSS Side

Define a hidden starting state and a visible end state in CSS. The JavaScript only toggles a class; the transition is pure CSS, which keeps it smooth.

// .reveal { opacity: 0; transform: translateY(20px);
//   transition: opacity 0.6s, transform 0.6s; }
// .reveal.visible { opacity: 1; transform: none; }

All lessons in this course

  1. Observing Element Visibility
  2. Lazy Loading Images
  3. Infinite Scrolling
  4. Scroll-Triggered Animations
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