Using TypeScript Using TypeScript ℹ️ This section has been moved to Using TypeScript Chapter .

JSX support New .tsx file extension and as operator Using React Using other JSX framworks Output generation Intersection types Example Local type declarations Class expre...

Generators and Iteration for ES5/ES3 Iterators Generators New --downlevelIteration Async Iteration Async iterators Async Generators The for-await-of Statement Caveats Ge...

Optional catch clause variables Type assertion/cast syntax in checkJs /@ts-check mode Deduplicated and redirected packages The --preserveSymlinks compiler flag Optional ca...

Constant-named properties Example Example unique symbol Example Example Strict Class Initialization Definite Assignment Assertions Example Fixed Length Tuples Improved t...

Project References Tuples in rest parameters and spread expressions Rest parameters with tuple types Spread expressions with tuple types Generic rest parameters Example Optio...

Faster subsequent builds with the --incremental flag Composite projects outFile Higher order type inference from generic functions Improvements for ReadonlyArray and readonl...

Optional Chaining Nullish Coalescing Assertion Functions Better Support for never -Returning Functions (More) Recursive Type Aliases --declaration and --allowJs The useDefi...

Control Flow Analysis of Aliased Conditions and Discriminants Symbol and Template String Pattern Index Signatures Defaulting to the unknown Type in Catch Variables (--useUnknown...

About this Handbook How is this Handbook Structured Non-Goals Get Started About this Handbook Over 20 years after its introduction to the programming community, JavaScript is...