TypeScript 6.0 RC is Now Available
The release candidate for TypeScript 6.0 is now available, continuing the language's dominance as the standard for scalable JavaScript development. The update focuses on improved type inference and developer tooling, reinforcing its value for fast-moving startups that need to enforce code quality and minimize production bugs with minimal overhead.
This release serves as a crucial bridge to the upcoming TypeScript 7.0, which will feature a completely rewritten compiler in Go. The new Go-based implementation is designed to leverage native code speed and shared-memory multi-threading for significant performance improvements. TypeScript 6.0 is the final major release planned to use the current JavaScript-based compiler. Consequently, many changes in this version are focused on preparing for the transition to the new architecture in 7.0 to minimize friction for developers. The release candidate introduces several changes to default compiler options to better align with modern development practices. For instance, `rootDir` will now default to `.` and `types` will default to an empty array. A significant change is the deprecation of targeting `es5`, reflecting the widespread adoption of evergreen browsers and the declining need to transpile to much older JavaScript versions. Other deprecated items include module systems like AMD and UMD and the `baseUrl` configuration option. New features in 6.0 include support for `es2025` as a compilation target and library option. It also adds built-in types for the `Temporal` API, a modern date/time API expected to be part of the JavaScript language soon. This version also introduces a `--stableTypeOrdering` flag to help developers compare compiler outputs between the current JavaScript-based version and the future Go-based version. Additionally, it now includes built-in types for `RegExp.escape` and adds `dom.iterable` and `dom.asynciterable` to the DOM library.
