What’s new in TypeScript 4.0?

Support for Variadic Tuple Types

Labeled Tuple Elements

Implied property type from constructors

Other 4.0 TypeScript Changes

  • For large TypeScript projects using VSCode there were significant loading delays upward of one minute, this has been shaved down to a couple seconds by a partial loading experience in which only the current files the editor has open will be processed until the full language service is ready.
  • Smarter auto imports have been implemented to auto-include type dependencies that are not in the node_modules/@types folder. Before this, auto-imports from packages not in the node_modules/@types folder only worked after there was at least one explicit import somewhere else in the project.
  • Speed improvements when using build mode with --incremental and --noEmitOnError flags enabled, previously the build time with these flags has been very slow, as there was no information that was cached in the .tsbuildinfo file.
  • The JS Doc label /** @deprecated */ can now be used to signify to editors that certain declarations are deprecated. For instance, in VSCode the value would be shown with a strike-though.

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