Utility types (intro)

Last reviewed Jun 1, 2026 Content v20260601

Track mode

client_typescript

Means

In-browser TS

Reading

~1 min

Level

intermediate

This lesson

An orientation to this TypeScript lesson—scope, vocabulary, and what you will practice next.

You need a clear map of the TypeScript track so later lessons do not feel like isolated tricks.

You will apply Utility types (intro) in contexts like: Modern front-end apps, Node APIs, and any team that standardizes on TS-first tooling.

Write TypeScript, compile in the browser, run the emitted JavaScript, and check understanding with MCQs. Also open the interview prep blocks.

Start here at the beginning of the typescript track before skipping ahead.

Built-ins transform types: Partial<T>, Pick<T, Keys>, Omit<T, Keys>, Record<K, V>.

Everyday combinations

Partial<Pick<User, 'name' | 'email'>> for PATCH payloads
Record<Role, string[]> for permission maps
Omit<User, 'passwordHash'> for public DTOs

More built-ins

Required<T> and Readonly<T> flip optionality and mutability for every property—handy when adapting DTOs between layers without rewriting interfaces by hand.

Self-check

Build a type for “create user” that omits id from User.

Utility types are pure type-level—they disappear in emitted JavaScript, so there is zero runtime cost.

Practice: Apply utility-types-intro in the playground, then explain utility types intro in one sentence without looking at notes.

Playground

Runs in your browser in a sandboxed frame. Backend runners appear when this track’s profile allows them.

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