Typescript

Statically typed superset of JavaScript that compiles to plain JavaScript. Adds an optional type layer for early error detection, improved editor tooling, and safer refactoring while keeping full compatibility with the JavaScript ecosystem.

Backed by Microsoft and adopted by major frameworks such as React, Vue, Angular, Svelte, and NestJS. Unlike Flow or JSDoc-only approaches, it offers a dedicated syntax for types plus inference that minimizes annotations. Gradual adoption lets teams add types incrementally: existing JavaScript is valid TypeScript, and JSDoc or .ts files can be introduced file by file. The compiled output runs anywhere JavaScript runs: browsers, Node.js, Deno, and Bun.

Key capabilities:

• Structural type system with interfaces, unions, generics, and literal types
• Type inference that understands JavaScript and reduces explicit annotations
• Gradual adoption: valid JavaScript is valid TypeScript, migrate incrementally
• Compiles to ES3 through latest ECMAScript for any target runtime
• Editor support: autocomplete, go-to-definition, refactoring, and error highlighting

Teams use it for large codebases and shared libraries where type safety catches bugs before runtime. API contracts and SDKs benefit from exported types that consumers can rely on. Full-stack developers keep types consistent across frontend and backend, and frameworks ship first-class TypeScript support with generated types and tsconfig presets.