Browser & Web Performance · Middle · Question 35 of 75

What does tree shaking rely on to remove unused code?

✓Correct answer: Static ES module import/export syntax, which can be analyzed at build time
2The defer attribute
3Runtime profiling in the browser

Explanation

CommonJS require is dynamic, so bundlers often can't prove code is unused. Side effects in modules also block removal.

Further reading

web.dev: Reduce JavaScript payloads with tree shaking ↗

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