TypeScript

TypeScript is a statically typed superset of JavaScript, developed by Microsoft and first released in 2012. Any valid JavaScript is valid TypeScript: the language adds optional type annotations that are checked at compile time and then erased, producing standard JavaScript that runs in any browser or JavaScript runtime.

Type inference means you rarely need to annotate every variable explicitly; TypeScript works out types from assignment, function signatures, and control flow. Interfaces and type aliases describe the shape of objects; generics create reusable components that work across types; utility types (Partial<T>, Readonly<T>, Pick<T, K>) handle common type transformations without boilerplate. The strict mode flag enables null safety and the full suite of checks, removing a whole class of runtime errors.

TypeScript has become the default for large JavaScript projects. Angular is TypeScript-first; React, Vue, and Svelte all have strong TS support, and DefinitelyTyped provides community-maintained type definitions for thousands of JavaScript libraries. Node.js, Deno, and Bun can run TypeScript files directly by stripping types, so small scripts no longer need a build step.

TypeScript 7 replaced the original JavaScript-based compiler with a native port written in Go, which type-checks large codebases roughly ten times faster with the same semantics. The compiler ships as an npm package and integrates with every major bundler and editor.