TypeScript

TypeScript is a free and open-source programming language developed by Microsoft that adds static types to JavaScript. A developer can declare what kind of value each variable, function argument and object should hold; the TypeScript compiler checks those types to catch mistakes before the code runs, then turns ("transpiles") the code into plain JavaScript. The result runs anywhere JavaScript does: in web browsers, on servers with Node.js, and in other runtimes. Because any valid JavaScript program is also valid TypeScript, existing projects can adopt it a file at a time. It is released under the Apache License 2.0 and developed in the open on GitHub.

History

TypeScript was designed by Anders Hejlsberg, the creator of Turbo Pascal and Delphi and lead architect of C#, and was first released publicly in October 2012. It grew from a Microsoft tool into the usual way to write large JavaScript applications, used by most major web frameworks and by editors such as Visual Studio Code for their code completion. By October 2026 the typescript package was being downloaded more than 300 million times a week from npm.

In March 2025 Microsoft announced it was porting the TypeScript compiler from TypeScript itself to the Go language, for builds roughly ten times faster. TypeScript 6.0, released in March 2026, was the last version built on the original JavaScript-based compiler. TypeScript 7.0, the first built on the native Go compiler, followed in July 2026.

Use

Node.js can run TypeScript files directly since version 22.18 (July 2025), by stripping out the type annotations without checking them, and the Deno runtime has run TypeScript natively since its first release. TypeScript is also the main language of many newer developer tools built for AI coding agents, including T3 Code and Lakebed, both from Ping Labs. Software engineer and YouTuber Theo Browne (T3) is well known for TypeScript-focused videos and for the "T3 Stack", a popular starter set of TypeScript web tools, and Boris Cherny, who later created Claude Code, wrote the O'Reilly book Programming TypeScript (2019).