Infinite Image Gallery

Overview

Create an image gallery that loads images as the user scrolls, arranged in a masonry (waterfall) layout. Images lazy-load as they enter the viewport, clicking opens a lightbox with zoom and navigation, and the layout adapts to screen width (1-4 columns).

The infinite image gallery combines several performance optimization techniques that are essential for modern web development. Masonry layout, lazy loading, intersection observer, responsive images, and virtualization are all patterns that appear in production image-heavy applications at companies like Pinterest, Unsplash, Instagram, and Flickr. Building this project gives you hands-on experience with each.

The masonry layout algorithm is particularly interesting: unlike a regular CSS Grid where all rows have the same height, masonry arranges items by placing each new image in the shortest column. This creates the distinctive Pinterest waterfall effect where images of different aspect ratios fit together without gaps. Implementing this efficiently requires tracking column heights and recalculating on resize.

For interviews at design-focused companies and media platforms, this project demonstrates performance optimization skills that directly impact Core Web Vitals: Largest Contentful Paint (lazy loading defers off-screen images), Cumulative Layout Shift (aspect ratio placeholders prevent layout jumps), and Interaction to Next Paint (virtualization keeps the DOM lean). These are the metrics that Google uses for search ranking and that product teams obsess over.

Interview questions

• CSS columns vs JS-calculated masonry?
• How do I implement lazy loading?
• How should the lightbox work?
• How do I handle responsive breakpoints?
• How do I prevent layout shift when images load?
• How do I virtualize a very large gallery?

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