TypeScript tutorialLesson 12Free preview

TS Union Types

This lesson is part of TypeScript · All levels

Summary

Union type combines several types with pipe markings so a value can be one of them. Before using a special property, the type must be narrowed down through a check. Discriminated unions help distinguish data variants through marker properties such as kind or type.

Key points

Union is written with a pipe mark.
Mandatory narrowing before access to special property
Discriminated unions use marker property

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