TypeScript 6.0 arrives

TypeScript 6.0 is slated to be the last release of the language based on the current JavaScript codebase and is now generally available. Version 6.0 acts as a bridge between TypeScript 5.9 and the planned TypeScript 7.0, close to completion and set to be speedier and based on the Go language.

The 6.0 production release was unveiled on March 23, following the release candidate that arrived March 6. Developers can access TypeScript 6.0 via NPM with the following command: npm install -D typescript.

TypeScript has been established as JavaScript with syntax for types. Several changes were cited as noteworthy additions in the general production release of TypeScript 6.0, including an adjustment in type-checking for function expressions in generic calls, especially those occurring in generic JSX expressions. This typically will catch more bugs in existing code, although developers may find that some generic calls may need an explicit type argument, said Daniel Rosenwasser, principal product manager for TypeScript at Microsoft.

Also, Microsoft has extended its deprecation of import assertion syntax (i.e. import ... assert {...}) to import() calls like import(..., { assert: {...}}).

With the general release, Microsoft also has updated the DOM types to reflect the latest web standards, including some adjustments to the Temporal APIs. Other capabilities featured in TypeScript 6.0  include:

• There is less context sensitivity on this-less functions. If this is never actually used in a function, then it is not considered contextually sensitive, which means these functions will be seen as higher priority when it comes to type inference.
• A new flag has been introduced, called –stableTypeOrdering , which is intended to assist with TypeScript 6.0 migrations to Version 7.0.
• TypeScript 6.0 adds support for the es2025option for both target and lib. Although there are no new JavaScript language features in ES2025, this new target adds new types for built-in APIs and moves a few declarations from esnext into es2025.
• The contents of lib.dom.iterable.d.tsand lib.dom.asynciterable.d.ts are included in lib.dom.d.ts. Developers still can reference dom.iterable and dom.asynciterable in a configuration file’s "lib" array, but they are now just empty files. TypeScript’s liboption lets users specify which global declarations a target runtime has.
• In TypeScript 6.0, usingmodule where namespacewas expected is now a hard deprecation. This change was necessary because module blocks are a potential ECMAScript proposal that would conflict with the legacy TypeScript syntax.

The foundation of TypeScript 7.0, meanwhile, is set to be a compiler and language service written in Go that takes advantage of the speed of native code and shared-memory multi-threading. Version 7.0 is “extremely close to completion,” Rosenwasser said. It can be tried out from the Visual Studio Code editor or installed via NPM. “In fact, if you’re able to adopt TypeScript 6.0, we encourage you to try out the native previews of TypeScript 7.0,” Rosenwasser said.