Type Widening and Type Narrowing in TypeScript

TypeScript internally makes use of type widening and type narrowing. Type narrowing reduces the possibilities of values which a variable can take. The opposite case is called type widening. This video shows you these special cases and how to work with them.

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Timeline:
00:00 Wide Types & Narrow Types
02:10 Type Widening & Type Narrowing
02:46 Type Widening in Variables
05:45 Type Widening in Arrays
07:37 Type Widening in Functions
09:55 Type Narrowing for union types
13:34 Type Widening in Literals

TypeScript errors being shown: TS2322, TS2345 & TS2367.

Resources:
➜ https://github.com/microsoft/TypeScript-New-Handbook/blob/master/reference/Widening-and-Narrowing.md
➜ https://github.com/Microsoft/TypeScript/pull/10676

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Тэги:

#typescript

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