| TypeScript | |
|---|---|
 | |
| Paradigm | Multi-paradigm:functional,generic,imperative,object-oriented |
| Family | ECMAScript |
| Designed by | Microsoft, Anders Hejlsberg, Luke Hoban |
| Developer | Microsoft |
| First appeared | 1 October 2012; 13 years ago (2012-10-01)[1] |
| Stable release | |
| Typing discipline | Duck,gradual,strong,structural[3] |
| Scope | Lexical |
| License | Apache 2.0 |
| Filename extensions | .ts, .tsx, .mts, .cts |
| Website | www |
| Influenced by | |
| C#,F#,[4]Java,JavaScript,ActionScript[5] | |
| Influenced | |
| AtScript,AssemblyScript,ArkTS | |
TypeScript (TS) is ahigh-levelprogramming language that addsstatic typing with optional typeannotations toJavaScript. It is designed for developing large applications. Ittranspiles to JavaScript.[6] It is developed byMicrosoft asfree and open-source software released under anApache License 2.0.
TypeScript may be used to develop JavaScript applications for bothclient-side andserver-side execution (as withReact.js,Node.js,Deno orBun). Multiple options are available for transpiling. The default TypeScript Compiler can be used,[7] or theBabel compiler can be invoked to convert TypeScript to JavaScript.
TypeScript supports definition files that can contain type information of existing JavaScriptlibraries, much likeC++header files can describe the structure of existingobject files. This enables other programs to use the values defined in the files as if they were statically typed TypeScript entities. There are third-party header files for popular libraries such asjQuery,MongoDB, andD3.js. TypeScript headers for theNode.js library modules are also available, allowing development of Node.js programs within TypeScript.[8]
The TypeScript compiler iswritten in TypeScript andcompiled to JavaScript. It is licensed under theApache License 2.0.Anders Hejlsberg, lead architect ofC# and creator ofDelphi andTurbo Pascal, has worked on developing TypeScript.[9][10][11][12]
TypeScript was released to the public in October 2012, with version 0.8, after two years of internal development at Microsoft.[13][14] Soon after the initial public release,Miguel de Icaza praised the language, but criticized the lack of matureintegrated development environment (IDE) support apart fromMicrosoft Visual Studio, which was unavailable then onLinux andmacOS.[15][16] As of April 2021 there is support in other IDEs and text editors, includingEmacs,Vim,WebStorm,Atom[17] and Microsoft's ownVisual Studio Code.[18] TypeScript 0.9, released in 2013, added support forgenerics.[19]
TypeScript 1.0 was released at Microsoft'sBuild developer conference in 2014.[20]Visual Studio 2013 Update 2 provided built-in support for TypeScript.[21] Further improvement were made in July 2014, when the development team announced a new TypeScript compiler, asserted to have a five-fold performance increase. Simultaneously, the source code, which was initially hosted onCodePlex, was moved toGitHub.[22]
On 22 September 2016, TypeScript 2.0 was released, introducing several features, including the ability for programmers to optionally enforcenull safety,[23] to mitigate what's sometimes referred to as thebillion-dollar mistake.
TypeScript 3.0 was released on 30 July 2018,[24] bringing many language additions like tuples in rest parameters and spread expressions, rest parameters with tuple types, generic rest parameters and so on.[25]
TypeScript 4.0 was released on 20 August 2020.[26] While 4.0 did not introduce any breaking changes, it added language features such as CustomJSX Factories and Variadic Tuple Types.[26]
TypeScript 5.0 was released on 16 March 2023 and included support for decorators.[27]
On March 11, 2025, Anders Hejlsberg announced on the TypeScript blog that the team is working on aGo port of the TypeScript compiler to be released as TypeScript version 7.0 later this year. It is expected to feature a 10xspeedup.[28]
TypeScript originated from the shortcomings of JavaScript for developing large-scale applications both at Microsoft and among their external customers.[29] Challenges with dealing with complex JavaScript code led to demand for custom tooling to ease developing of components in the language.[30]
Developers sought a solution that would not break compatibility with theECMAScript (ES) standard and its ecosystem, so acompiler was developed to transform a superset of JavaScript with type annotations and classes (TypeScript files) back into vanilla ECMAScript 5 code. TypeScript classes were based on the then-proposed ECMAScript 6 class specification to make writingprototypal inheritance less verbose and error-prone, and type annotations enabledIntelliSense and improved tooling.
TypeScript adds the following syntax extensions to #"/wiki/Type_signature" title="Type signature">Type signatures (annotations) andcompile-timetype checking
Syntactically, TypeScript is very similar toJScript .NET, another Microsoft implementation of the ECMA-262 language standard that added support for static typing and classical object-oriented language features such as classes, inheritance, interfaces, and namespaces. Other inspirations includeJava andC#.
As TypeScript is simply a superset of JavaScript, existing JavaScript can be adapted to TypeScript and TypeScript program can seamlessly consume JavaScript. The compiler can target all ECMAScript versions 5 and above, transpiling modern features like classes and arrow functions to their older counterparts.
With TypeScript, it is possible to use existing JavaScript code, incorporate popular JavaScript libraries, and call TypeScript-generated code from other JavaScript.[32] Type declarations for these libraries are usually provided with the source code but can be declared or installed separately if needed.
The TypeScript compiler, namedtsc, iswritten in TypeScript. As a result, it can be compiled into regular JavaScript and can then be executed in any JavaScript engine (e.g. a browser). The compiler package comes bundled with a script host that can execute the compiler. It is also available as aNode.js package that uses Node.js as a host.
The compiler cantarget a given edition of ECMAScript (such asECMAScript 5 for legacy browser compatibility), but by default compiles for the latest standards.
Usingplug-ins, TypeScript can be integrated withbuild automation tools, including Grunt (grunt-ts[38]),Apache Maven (TypeScript Maven Plugin[39]), Gulp (gulp-typescript[40]) andGradle (TypeScript Gradle Plugin[41]).
TSLint[42] scans TypeScript code for conformance to a set of standards and guidelines.ESLint, a standard JavaScript linter, also provided some support for TypeScript via community plugins. However, ESLint's inability to leverage TypeScript's language services precluded certain forms of semantic linting and program-wide analysis.[43] In early 2019, the TSLint team announced the linter's deprecation in favor oftypescript-eslint, a joint effort of the TSLint, ESLint and TypeScript teams to consolidate linting under the ESLint umbrella for improved performance, community unity and developer accessibility.[44]
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| Version number | Release date | Significant changes |
|---|---|---|
| Unsupported: 0.8 | 1 October 2012 (2012-10-01) | |
| Unsupported: 0.9 | 18 June 2013 (2013-06-18) | |
| Unsupported: 1.0 | 12 April 2014 (2014-04-12) | |
| Unsupported: 1.1 | 6 October 2014 (2014-10-06) | performance improvements |
| Unsupported: 1.3 | 12 November 2014 (2014-11-12) | protected modifier, tuple types |
| Unsupported: 1.4 | 20 January 2015 (2015-01-20) | union types,let andconst declarations, template strings, type guards, type aliases |
| Unsupported: 1.5 | 20 July 2015 (2015-07-20) | ES6 modules,namespace keyword,for..of support, decorators |
| Unsupported: 1.6 | 16 September 2015 (2015-09-16) | JSX support,intersection types, local type declarations,abstract classes and methods, user-defined type guard functions |
| Unsupported: 1.7 | 30 November 2015 (2015-11-30) | async andawait support, |
| Unsupported: 1.8 | 22 February 2016 (2016-02-22) | constraints generics, control flow analysis errors, string literal types,allowJs |
| Unsupported: 2.0 | 22 September 2016 (2016-09-22) | null- and undefined-aware types, control flow based type analysis, discriminated union types,never type,readonly keyword, type ofthis for functions |
| Unsupported: 2.1 | 8 November 2016 (2016-11-08) | keyof and lookup types, mapped types, object spread and rest, |
| Unsupported: 2.2 | 22 February 2017 (2017-02-22) | mix-in classes,object type, |
| Unsupported: 2.3 | 27 April 2017 (2017-04-27) | async iteration, generic parameter defaults, strict option |
| Unsupported: 2.4 | 27 June 2017 (2017-06-27) | dynamic import expressions, string enums, improved inference for generics, strict contravariance for callback parameters |
| Unsupported: 2.5 | 31 August 2017 (2017-08-31) | optional catch clause variables |
| Unsupported: 2.6 | 31 October 2017 (2017-10-31) | strict function types |
| Unsupported: 2.7 | 31 January 2018 (2018-01-31) | constant-named properties, fixed-length tuples |
| Unsupported: 2.8 | 27 March 2018 (2018-03-27) | conditional types, improvedkeyof with intersection types |
| Unsupported: 2.9 | 14 May 2018 (2018-05-14) | support for symbols and numeric literals inkeyof and mapped object types |
| Unsupported: 3.0 | 30 July 2018 (2018-07-30) | project references, extracting and spreading parameter lists with tuples |
| Unsupported: 3.1 | 27 September 2018 (2018-09-27) | mappable tuple and array types |
| Unsupported: 3.2 | 30 November 2018 (2018-11-30) | stricter checking forbind,call, andapply |
| Unsupported: 3.3 | 31 January 2019 (2019-01-31) | relaxed rules on methods of union types, incremental builds for composite projects |
| Unsupported: 3.4 | 29 March 2019 (2019-03-29) | faster incremental builds, type inference from generic functions,readonly modifier for arrays,const assertions, type-checking globalthis |
| Unsupported: 3.5 | 29 May 2019 (2019-05-29) | faster incremental builds, omit helper type, improved excess property checks in union types, smarter union type checking |
| Unsupported: 3.6 | 28 August 2019 (2019-08-28) | Stricter generators, more accurate array spread, better Unicode support for identifiers |
| Unsupported: 3.7 | 5 November 2019 (2019-11-05) | Optional chaining, nullish coalescing |
| Unsupported: 3.8 | 20 February 2020 (2020-02-20) | Type-only imports and exports, ECMAScript private fields, top-levelawait |
| Unsupported: 3.9 | 12 May 2020 (2020-05-12) | Improvements in inference, speed improvements |
| Unsupported: 4.0 | 20 August 2020 (2020-08-20) | Variadic tuple types, labeled tuple elements |
| Unsupported: 4.1 | 19 November 2020 (2020-11-19) | Template literal types, key remapping in mapped types, recursive conditional types |
| Unsupported: 4.2 | 25 February 2021 (2021-02-25) | Smarter type alias preservation, leading/middle rest elements in tuple types, stricter checks for thein operator,abstract construct signatures |
| Unsupported: 4.3 | 26 May 2021 (2021-05-26) | Separate write types on properties,override and the--noImplicitOverride flag, template string type improvements |
| Unsupported: 4.4 | 26 August 2021 (2021-08-26) | Control flow analysis of aliased conditions and discriminants, symbol and template string pattern index signatures |
| Unsupported: 4.5 | 17 November 2021 (2021-11-17) | Type and promise improvements, supporting lib fromnode_modules, template string types as discriminants, andes2022 module |
| Unsupported: 4.6 | 28 February 2022 (2022-02-28) | Type inference and checks improvements, support for ES2022 target, better ECMAScript handling |
| Unsupported: 4.7 | 24 May 2022 (2022-05-24) | Support for ES modules, instantiation expressions, variance annotations for type parameters, better control-flow checks and type check improvements |
| Unsupported: 4.8 | 25 August 2022 (2022-08-25) | Intersection and union types improvements, better type inference |
| Unsupported: 4.9 | 15 November 2022 (2022-11-15) | satisfies operator, auto-accessors in classes (proposal), improvements in type narrowing and checks |
| Unsupported: 5.0 | 16 March 2023 (2023-03-16) | ES decorators (proposal), type inference improvements,bundler module resolution mode, speed and size optimizations |
| Unsupported: 5.1 | 1 June 2023 (2023-06-01) | Easier implicit returns forundefined and unrelated types for getters and setters |
| Unsupported: 5.2 | 24 August 2023 (2023-08-24) | using declarations and explicit resource management, decorator metadata and named and anonymous tuple elements |
| Unsupported: 5.3 | 20 November 2023 (2023-11-20) | Improved type narrowing, correctness checks and performance optimizations |
| Unsupported: 5.4 | 6 March 2024 | Object.groupBy andMap.groupBy support |
| Unsupported: 5.5 | 20 June 2024 | Inferred Type Predicates, Regular Expression Syntax Checking, and Type Imports in JSDoc |
| Unsupported: 5.6 | 9 September 2024 | Advanced type inference, variadic tuple enhancements, partial module declarations. |
| Unsupported: 5.7 | 22 November 2024 | |
| Unsupported: 5.8 | 28 February 2025 | |
| Latest version:5.9 | 31 July 2025 | |
| Future version: 6.0 | Introduce some deprecations and breaking changes to align with the upcoming native codebase. | |
| Future version: 7.0 | Rewrite in Go with faster performance. |
TypeScript was directly influenced by F#: one of the originators of TypeScript was Luke Hoban, who began TypeScript (then called Strada) immediately after working on F# 2.0. Recently he noted the influence of F# on early parts of the TypeScript design [Hoban 2017].
But TypeScript only delivers half of the value in using a strongly typed language to Unix developers: strong typing. Intellisense, code completion and refactoring are tools that are only available to Visual Studio Professional users on Windows. There is no Eclipse, MonoDevelop or Emacs support for any of the language features.
And I think this is a pretty big misstep. If you're building web apps that run on anything other than Windows, you're likely using a Mac and most likely not using Visual Studio. You need the Visual Studio plug-in to get the IntelliSense. All you get without Visual Studio is the strong-typing. You don't get the productivity benefits you get from IntelliSense.
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