The TypeScript Handbook (2025 edition)

By Flavio Copes

The 2025 edition of my TypeScript Handbook is out, adding type guards, generics, as const assertions, and a clear explanation of unknown versus any.

I first released the first edition of the TypeScript Handbook last year, late 2024, and after updating the JavaScript Handbook today, I decided to do a good review of the TypeScript book as well.

I want to keep all books as up to date as possible, and TS is one of those things that are evolving rather quickly.

The handbook covers essential TypeScript features while remaining beginner-friendly and up-to-date with modern practices.

Here’s a concise changelog:

• Fixed some broken links
• Fixed grammar and typos
• Updated code style: single quotes, consistent spacing, number[] over Array<number>
• Explained unknown vs any
• Introduced the use of optional chaining & nullish coalescing
• Added type guards
• Introduced as const assertions
• Explained basic generics
• Added notes about TS runtime support (Bun/Deno/ts-node)

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