What is TypeScript? Why is it used in Angular?

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TypeScript is a strongly-typed superset of JavaScript developed by Microsoft. Compiles to plain JavaScript before running. Angular is built in TypeScript and strongly recommends it for application code. Static typing — catches type errors at compile time, before code runs. Better tooling — rich autocomplete, refactoring, navigation in IDEs (VS Code, WebStorm). Decorators — Angular relies on TypeScript decorators ( @Component , @Injectable ) for metadata. Interfaces and generics — describe data shapes and reusable contracts; useful for forms, services, HTTP responses. Self-documenting — types double as inline API documentation; teams onboard faster. Strict mode — strict: true in tsconfig catches null/undefined bugs early; Angular projects use it by default. Compiles down to JS — the browser only ever sees JavaScript. Three wins to name: compile-time types, decorators (Angular's metadata needs them), IDE tooling. Honest framing: TS is compile-time safety, not runtime — pair with Zod for API responses.