TypeScript 7: Microsoft accelerates 10x with Go

What happened?

Microsoft has published the release candidate of TypeScript 7, a version that represents a qualitative leap in the performance of the popular JavaScript superset. The key lies in the rewrite of the compiler and associated tools in Go, a compiled and efficient language, instead of the old compiler written in TypeScript/JavaScript. According to InfoWorld, early tests already showed a speedup close to 10x, and the RC confirms those expectations. This change is not trivial: the TypeScript team worked for over a year on this migration, since Microsoft announced its plans in mid-2024. Early experimental versions required manual compilation and were not suitable for production, but the current RC installs from npm like any other version, and includes a native preview of the language server for Visual Studio Code, available through an extension. Adoption has been massive: nearly half a million downloads to date, according to npm data.

Why is it important?

Performance has long been a weak point of TypeScript, especially in large projects or monorepos with multiple projects. Compilation and type-checking times could stretch to minutes, affecting productivity and the development experience. With TypeScript 7, those times are drastically reduced, enabling faster iterations and smoother continuous integration. Historically, TypeScript has been criticized for being slow compared to alternatives like Flow (from Facebook) or even plain JavaScript with JSDoc. The switch to Go, a language designed for concurrent systems, allows more efficient parallelization: TypeScript 7 can launch multiple type-checking workers that work simultaneously, albeit with corresponding memory and CPU consumption. Users can configure the number of workers to balance performance and resources. This approach is similar to what Google did with Dart when rewriting its compiler in C++ or Rust, or Go itself in the past. Microsoft's decision to use Go instead of Rust (as it did with parts of Windows) or C++ is likely due to the team's familiarity with Go and its mature ecosystem for command-line tools.

What consequences will it have?

For developers, the main consequence is a notable improvement in development speed. Projects that previously took several seconds to compile will now do so in fractions of a second. This not only improves the experience but also enables more responsive tools and more immediate feedback. In the enterprise, adopting TypeScript 7 can reduce CI/CD infrastructure costs by shortening build times, and improve team morale by eliminating frustrating waits. However, migration is not trivial. TypeScript 7 introduces significant changes to the language and configuration compared to TypeScript 5 (TypeScript 6 serves as an intermediate step for experimentation). Microsoft recommends reading the RC documentation and using the VS Code extension to guide the update. Additionally, parallelization can increase resource consumption on local machines and CI servers, which may require adjustments to hosting plans or runner configurations. Large monorepos, such as those at tech companies that extensively use TypeScript (Google, Meta, Airbnb), are expected to be early adopters, though they will need to carefully test compatibility with their internal tools. Competition will also intensify: Deno and Bun already offer native runtimes for TypeScript, and Microsoft's performance improvement could further consolidate TypeScript as the de facto standard for large-scale web development.

What should readers know?

• Performance: The speedup is real and significant, but depends on project size and parallelization settings. In Microsoft's internal tests, projects like the TypeScript compiler itself went from 25 seconds to 2 seconds in incremental mode.
• Compatibility: TypeScript 7 is a major change; it is recommended to test in an isolated environment before migrating production projects. Some internal APIs have changed, so tools like ts-jest or ts-node may need updates.
• Tools: The native VS Code extension is key to fully leveraging the new capabilities. It is in preview, but Microsoft publishes new versions almost daily.
• Resources: Parallelization consumes more memory and CPU; workers should be adjusted based on available hardware. By default, TypeScript 7 uses as many workers as CPU cores, but can be limited with the --workers option.
• Future: Microsoft continues to develop the Go compiler, with new language server versions almost daily. The stable release is expected by mid-2025, and TypeScript 8 is already being planned with more native optimizations.

"TypeScript 7 represents a milestone in the evolution of the language, demonstrating that betting on a native runtime can revolutionize the developer experience. Reducing compilation times from minutes to seconds not only improves productivity but enables more agile workflows and better integration with CI/CD tools."