Tree Shaking React Native Apps
Article Summary
Klarna Engineering borrowed a web optimization technique and cut their React Native app startup time by 20%. Here's how tree shaking made the difference.
The Klarna team applied tree shaking (dead-code elimination) to their React Native app, tackling technical challenges around module systems and syntax compatibility. This detailed implementation guide shows how web bundling techniques can dramatically improve mobile performance.
Key Takeaways
- Tree shaking works best with ES modules, not CommonJS (static analysis matters)
- Critical JavaScript chunk reduced by 46%, overall bundle down 14%
- Samsung Galaxy S9 startup improved from 2.8s to 2.2s in production
- Build times increased 30% but user experience gains justified the tradeoff
- TypeScript's isolatedModules flag fixed invalid re-export issues
By implementing tree shaking in React Native, Klarna achieved a 20% median startup improvement and 46% smaller critical bundle, proving web optimization techniques translate to mobile.
About This Article
Klarna's React Native app had a module system problem. React Native mixed CommonJS and ES modules together, which broke Webpack's ability to detect exports and remove dead code.
The team fixed the syntax issues by turning on TypeScript's isolatedModules flag and adding type modifiers to imports. They also made sure that dependencies used modern ES module syntax so Hermes could process them without extra transpilation.
The changes increased build times to 4 minutes total, a 30% increase from before. However, the JavaScript bundle shrank by 14% overall across the entire application.