ignitae Academy

TypeScript for JavaScript developers

TypeScript without the ceremony: annotations, narrowing, generics and the built-in type operators, starting from real JavaScript.

Syllabus

Annotations and inference

Say the type where it can't be guessed, let inference do the rest
Cart totals: annotate the inputs, infer the rest (exercise)

unknown vs any

unknown makes you check; any makes you lie
Safe JSON: narrow unknown, don't trust any (exercise)

Unions and narrowing

A union is a set of shapes, narrowed by a tag
Input events: a union narrowed by a tag (exercise)

Generics 101

A generic keeps the relationship between input and output
first, last and identity: generics that keep the type (exercise)

Utility types

Built-in type operators beat hand-writing every variant
User drafts: Partial, Readonly and Record in practice (exercise)