TL;DR

TypeScript 6.0.3 improves code completion and error reporting when using decorators (code modifiers) by addressing a regression introduced in v6.0.2.

Fixes Worth Knowing

Code completion now functions correctly with decorators. Error messages related to decorator usage are more accurate and helpful.

TL;DR

TypeScript 6.0 improves type checking and developer experience with enhanced support for decorators (code annotations) and organizational tooling.

Fixes Worth Knowing

Numerous fixes address issues reported during the 6.0 beta and release candidate phases, improving overall stability and reliability.

Before You Upgrade

Review the TypeScript 6.0 release announcement for detailed information on changes and potential impacts to your projects: https://devblogs.microsoft.com/typescript/announcing-typescript-6-0-rc/.

TL;DR

TypeScript 5.9 improves code completion and error reporting, offering a more robust development experience.

Breaking

None.

New

None.

Fixes Worth Knowing

Multiple bug fixes across versions 5.8 and 5.9 address issues reported by the community, improving overall stability and reliability of the compiler (code translator).

Before You Upgrade

No specific action is needed; these are bug fix releases.

TL;DR

TypeScript 5.9 improves type checking accuracy and developer experience with several bug fixes addressing issues reported during beta testing.

Breaking

[None]

New

[None]

Fixes Worth Knowing

Numerous fixes improve the stability and correctness of type inference, particularly around complex generic types and conditional types. These improvements should reduce unexpected type errors in your code.

Before You Upgrade

No specific action is needed; update to the latest TypeScript version via npm.

TL;DR

TypeScript 4.9 introduces improved editor support and developer experience with enhanced satisfaction reports, though no major feature changes are present in these release candidates.

Breaking

None.

New

None.

Fixes Worth Knowing

None.

Before You Upgrade

No action is needed for these release candidates; they are for testing purposes only.

TL;DR

TypeScript now provides more consistent behavior around deprecated features, and a fix improves timestamp handling in certain scenarios.

Breaking

• Deprecation messages related to ignore are now consistent across TypeScript versions (warnings about outdated code).

Fixes Worth Knowing

• Timestamp handling is corrected, resolving issues with date/time representations (data serialization).

Before You Upgrade

No specific action is needed for this update.

TL;DR

TypeScript now performs significantly faster, especially when used with Node.js 16, resolving a recent performance slowdown.

Fixes Worth Knowing

TypeScript compilation is faster, particularly in projects utilizing Node.js 16 (JavaScript runtime).

Before You Upgrade

No action is needed; this is a performance improvement release.

TL;DR

TypeScript 3.9 improves type checking with support for optional chaining and the nullish coalescing operator (JavaScript features), enabling more concise and safer code.

Breaking

• Optional chaining and nullish coalescing now require strictNullChecks to be enabled. (Compiler flags)

New

• Optional chaining (?.) and the nullish coalescing operator (??) are now supported. (JavaScript syntax)
• Improved performance for large projects. (Build speed)

Fixes Worth Knowing

• Fixed an issue where auto-imports would sometimes fail. (Code editor assistance)

Before You Upgrade

• Enable the strictNullChecks compiler option if you plan to use optional chaining or the nullish coalescing operator.

TL;DR

This release improves TypeScript’s stability with numerous bug fixes addressing issues reported in the previous version.

Breaking

[None]

New

[None]

Fixes Worth Knowing

Numerous bugs have been fixed, improving overall code compilation and editor experience.

Before You Upgrade

If using Visual Studio 2017, select the new TypeScript version in Tools/Options after updating.

TL;DR

TypeScript 2.9 improves static checking with default-only parameters and more precise intersection/union types, helping you catch errors earlier.

Breaking

• typeof for function types now includes parameter lists (may affect type guards).
• --useUnknownInCatchVariables is now on by default (strict error checking for catch clause variables).

New

• Default-only parameters (function arguments can require a default value).
• Improved intersection/union type inference (more accurate type narrowing).

Fixes Worth Knowing

• Fixes an issue where some mapped types were incorrectly inferred as any.

Before You Upgrade

• If you rely on the previous behavior of typeof for function types, review your type guards.

TL;DR

TypeScript now correctly handles JSX spread attributes (React components) without relying on internal React APIs, ensuring compatibility with React 15 and later.

Breaking

• JSX spread attributes (React component props) now emit a standalone helper function, potentially requiring updates to existing build processes if they relied on the previous internal implementation.

Fixes Worth Knowing

• Resolved an issue causing errors when using JSX spread attributes with recent React versions.

Before You Upgrade

• Verify your build process isn't directly referencing the prior internal React helper function for JSX spread attributes.

TL;DR

TypeScript 1.8 improves support for large projects with more accurate and faster type checking via structural typing and control flow analysis.

Breaking

• Structural typing for classes (class compatibility based on shape) may change existing behavior if relying on nominal typing.
• Control flow analysis (how the compiler understands program logic) is more strict, potentially flagging previously unflagged errors.

New

• Structural typing for classes allows more flexible code reuse.
• Improved control flow analysis leads to more accurate type checking.

Fixes Worth Knowing

• Fixes for various edge cases in type inference and error reporting.

Before You Upgrade

• Review code relying on nominal typing for classes to ensure compatibility with structural typing.

TL;DR

TypeScript now supports ES6 generators, enabling more concise asynchronous code and improved iteration patterns.

New

• ES6 Generators: Allows writing asynchronous code in a more synchronous style (iterators for sequences).

Fixes Worth Knowing

• Improved error reporting for ambiguous code, making debugging easier.
• Fixed a bug where certain complex generic types could cause compiler crashes.

Before You Upgrade

• Review code using older iteration patterns to see if generators offer a more readable alternative.