
# TypeScript

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[TypeScript](https://www.typescriptlang.org/) is a language for application-scale JavaScript. TypeScript adds optional types to JavaScript that support tools for large-scale JavaScript applications for any browser, for any host, on any OS. TypeScript compiles to readable, standards-based JavaScript. Try it out at the [playground](https://www.typescriptlang.org/play/), and stay up to date via [our blog](https://blogs.msdn.microsoft.com/typescript) and [Twitter account](https://twitter.com/typescript).

Find others who are using TypeScript at [our community page](https://www.typescriptlang.org/community/).

## Installing

For the latest stable version:

```bash
npm install -g typescript
```

For our nightly builds:

```bash
npm install -g typescript@next
```

## Contribute

There are many ways to [contribute](https://github.com/microsoft/TypeScript/blob/master/CONTRIBUTING.md) to TypeScript.
* [Submit bugs](https://github.com/microsoft/TypeScript/issues) and help us verify fixes as they are checked in.
* Review the [source code changes](https://github.com/microsoft/TypeScript/pulls).
* Engage with other TypeScript users and developers on [StackOverflow](https://stackoverflow.com/questions/tagged/typescript).
* Help each other in the [TypeScript Community Discord](https://discord.gg/typescript).
* Join the [#typescript](https://twitter.com/search?q=%23TypeScript) discussion on Twitter.
* [Contribute bug fixes](https://github.com/microsoft/TypeScript/blob/master/CONTRIBUTING.md).
* Read the language specification ([docx](https://github.com/microsoft/TypeScript/blob/master/doc/TypeScript%20Language%20Specification.docx?raw=true),
 [pdf](https://github.com/microsoft/TypeScript/blob/master/doc/TypeScript%20Language%20Specification.pdf?raw=true), [md](https://github.com/microsoft/TypeScript/blob/master/doc/spec.md)).

This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see
the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com)
with any additional questions or comments.

## Documentation

*  [TypeScript in 5 minutes](https://www.typescriptlang.org/docs/handbook/typescript-in-5-minutes.html)
*  [Programming handbook](https://www.typescriptlang.org/docs/handbook/basic-types.html)
*  [Language specification](https://github.com/microsoft/TypeScript/blob/master/doc/spec.md)
*  [Homepage](https://www.typescriptlang.org/)

## Building

In order to build the TypeScript compiler, ensure that you have [Git](https://git-scm.com/downloads) and [Node.js](https://nodejs.org/) installed.

Clone a copy of the repo:

```bash
git clone https://github.com/microsoft/TypeScript.git
```

Change to the TypeScript directory:

```bash
cd TypeScript
```

Install [Gulp](https://gulpjs.com/) tools and dev dependencies:

```bash
npm install -g gulp
npm ci
```

Use one of the following to build and test:

```
gulp local             # Build the compiler into built/local.
gulp clean             # Delete the built compiler.
gulp LKG               # Replace the last known good with the built one.
                       # Bootstrapping step to be executed when the built compiler reaches a stable state.
gulp tests             # Build the test infrastructure using the built compiler.
gulp runtests          # Run tests using the built compiler and test infrastructure.
                       # Some low-value tests are skipped when not on a CI machine - you can use the
                       # --skipPercent=0 command to override this behavior and run all tests locally.
                       # You can override the specific suite runner used or specify a test for this command.
                       # Use --tests=<testPath> for a specific test and/or --runner=<runnerName> for a specific suite.
                       # Valid runners include conformance, compiler, fourslash, project, user, and docker
                       # The user and docker runners are extended test suite runners - the user runner
                       # works on disk in the tests/cases/user directory, while the docker runner works in containers.
                       # You'll need to have the docker executable in your system path for the docker runner to work.
gulp runtests-parallel # Like runtests, but split across multiple threads. Uses a number of threads equal to the system
                       # core count by default. Use --workers=<number> to adjust this.
gulp baseline-accept   # This replaces the baseline test results with the results obtained from gulp runtests.
gulp lint              # Runs eslint on the TypeScript source.
gulp help              # List the above commands.
```


## Usage

```bash
node built/local/tsc.js hello.ts
```


## Roadmap

For details on our planned features and future direction please refer to our [roadmap](https://github.com/microsoft/TypeScript/wiki/Roadmap).
