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TypeScript at Application Boundaries
Pause here and make sure the main ideas feel clear before moving to the next chapter.
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What you should understand now
Use TypeScript safely with external data, modules, React, and library declarations.
Unknown data and runtime validation
Validate data that TypeScript cannot trust.
Declaration files and module types
Describe JavaScript libraries and non-code imports.
Strictness and safe migration
Adopt TypeScript without hiding uncertainty.
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