Pretext.js

Pretext.js is a high-performance text layout library that solves the critical performance bottleneck of DOM-based text measurement. Traditional methods like getBoundingClientRect() trigger forced synchronous reflows, causing significant slowdowns in text-heavy applications. Pretext.js eliminates this by using pure arithmetic for layout calculations after an initial preparation phase.

Key Features:

• Zero DOM Reads: After the initial prepare() call, all layout() operations are pure arithmetic with no DOM access
• Real Font Metrics: Uses Canvas measureText() for accurate glyph width measurements matching browser rendering
• Multilingual Support: Handles CJK, Arabic, Hebrew, Thai, Hindi, Korean, and other writing systems with proper Unicode segmentation
• TypeScript-First: Built with TypeScript from the ground up with precise type definitions
• Framework-Agnostic: Works with any JavaScript framework or vanilla JS
• Zero Dependencies: No external packages required

Use Cases:

• Virtual scrolling lists with variable-height items
• AI chat interfaces with streaming responses
• Multilingual content feeds and social platforms
• Code editors and text-heavy UIs
• Any application where text layout performance is critical

How It Works:

1. Prepare: Normalize text, apply Unicode rules, and measure glyphs using Canvas (runs once)
2. Layout: Compute line breaks and heights through arithmetic (instant, no DOM)
3. Reuse: Same prepared handle works for any container width

Performance: Measures 1,000 text blocks in ~2ms with 0 DOM reads, compared to ~94ms with traditional methods.