Answer
Fetching causes side effects. Render and constructors must remain pure, so fetching should occur in effects or server loaders.
Quick Answer
Constructors and render methods run synchronously and block painting. Fetching data there delays the initial render. It also causes bugs in concurrent mode where React may run render multiple times. Data fetching belongs in effects, server-side data loaders, or Suspense-compatible libraries that integrate with React's rendering lifecycle.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ