JavaScript Performance · AuditJet Glossary

Tree Shaking

A dead code elimination technique used by JavaScript bundlers to remove unused exports from the final bundle.

Tree shaking works by analysing the dependency graph of ES modules and removing any exports that are never imported. It's supported by Webpack, Rollup, and esbuild. Effective tree shaking requires using ES module syntax (import/export) rather than CommonJS. Unused library code is a common cause of bloated JavaScript bundles that inflate TBT and INP.

Related terms

Code Splitting

A technique that splits JavaScript bundles into smaller chunks that are loaded on demand rather than all at once.

TBT (Total Blocking Time)

The total time between First Contentful Paint and Time to Interactive during which the main thread was blocked for long enough to prevent input responsiveness.

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