TypeScript tutorialLesson 28Free preview

TS Conditional Types

This lesson is part of TypeScript · All levels

Summary

Conditional type decides type based on the relationship extends, with the pattern T extends U? X : Y. When T is a union, the conditional is distributive to each member. The infer operator is used to extract subtypes such as the type of argument or the return of a function.

Key points

The basic pattern: T extends U? X: Y
Union triggers conditional distributive
Infer captures a sub-type of the matched type

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