Please [read the FAQ](https://github.com/Microsoft/TypeScript/wiki/FAQ) before logging new issues, even if you think you have found a bug.
Issues that ask questions answered in the FAQ will be closed without elaboration.
## 2. Search for Duplicates
[Search the existing issues](https://github.com/Microsoft/TypeScript/issues?utf8=%E2%9C%93&q=is%3Aissue) before logging a new one.
## 3. Do you have a question?
The issue tracker is for **issues**, in other words, bugs and suggestions.
If you have a *question*, please use [Stack Overflow](http://stackoverflow.com/questions/tagged/typescript), [Gitter](https://gitter.im/Microsoft/TypeScript), your favorite search engine, or other resources.
Due to increased traffic, we can no longer answer questions in the issue tracker.
## 4. Did you find a bug?
When logging a bug, please be sure to include the following:
* What version of TypeScript you're using (run `tsc --v`)
* If at all possible, an *isolated* way to reproduce the behavior
* The behavior you expect to see, and the actual behavior
You can try out the nightly build of TypeScript (`npm install typescript@next`) to see if the bug has already been fixed.
## 5. Do you have a suggestion?
We also accept suggestions in the issue tracker.
Be sure to [check the FAQ](https://github.com/Microsoft/TypeScript/wiki/FAQ) and [search](https://github.com/Microsoft/TypeScript/issues?utf8=%E2%9C%93&q=is%3Aissue) first.
In general, things we find useful when reviewing suggestions are:
* A description of the problem you're trying to solve
* An overview of the suggested solution
* Examples of how the suggestion would work in various places
* Code examples showing e.g. "this would be an error, this wouldn't"
* Code examples showing the generated JavaScript (if applicable)
* If relevant, precedent in other languages can be useful for establishing context and expected behavior
# Instructions for Contributing Code
## Code of Conduct
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.
## Contributing bug fixes
TypeScript is currently accepting contributions in the form of bug fixes. A bug must have an issue tracking it in the issue tracker that has been approved ("Milestone == Community") by the TypeScript team. Your pull request should include a link to the bug that you are fixing. If you've submitted a PR for a bug, please post a comment in the bug to avoid duplication of effort.
## Contributing features
Features (things that add new or improved functionality to TypeScript) may be accepted, but will need to first be approved (marked as "Milestone == Community" by a TypeScript coordinator with the message "Approved") in the suggestion issue. Features with language design impact, or that are adequately satisfied with external tools, will not be accepted.
Design changes will not be accepted at this time. If you have a design change proposal, please log a suggestion issue.
## Legal
You will need to complete a Contributor License Agreement (CLA). Briefly, this agreement testifies that you are granting us permission to use the submitted change according to the terms of the project's license, and that the work being submitted is under appropriate copyright.
Please submit a Contributor License Agreement (CLA) before submitting a pull request. You may visit https://cla.microsoft.com to sign digitally. Alternatively, download the agreement ([Microsoft Contribution License Agreement.docx](https://www.codeplex.com/Download?ProjectName=typescript&DownloadId=822190) or [Microsoft Contribution License Agreement.pdf](https://www.codeplex.com/Download?ProjectName=typescript&DownloadId=921298)), sign, scan, and email it back to <cla@microsoft.com>. Be sure to include your github user name along with the agreement. Once we have received the signed CLA, we'll review the request.
## Housekeeping
Your pull request should:
* Include a description of what your change intends to do
* Be a child commit of a reasonably recent commit in the **master** branch
* Requests need not be a single commit, but should be a linear sequence of commits (i.e. no merge commits in your PR)
* It is desirable, but not necessary, for the tests to pass at each commit
* Have clear commit messages
* e.g. "Refactor feature", "Fix issue", "Add tests for issue"
* Include adequate tests
* At least one test should fail in the absence of your non-test code changes. If your PR does not match this criteria, please specify why
* Tests should include reasonable permutations of the target fix/change
* Include baseline changes with your change
* All changed code must have 100% code coverage
* Follow the code conventions described in [Coding guidelines](https://github.com/Microsoft/TypeScript/wiki/Coding-guidelines)
* To avoid line ending issues, set `autocrlf = input` and `whitespace = cr-at-eol` in your git configuration
## Contributing `lib.d.ts` fixes
The library sources are in: [src/lib](https://github.com/Microsoft/TypeScript/tree/master/src/lib)
Library files in `built/local/` are updated by running
```Shell
jake
```
The files in `lib/` are used to bootstrap compilation and usually do not need to be updated.
#### `src/lib/dom.generated.d.ts` and `src/lib/webworker.generated.d.ts`
These two files represent the DOM typings and are auto-generated. To make any modifications to them, please submit a PR to https://github.com/Microsoft/TSJS-lib-generator
## Running the Tests
To run all tests, invoke the `runtests-parallel` target using jake:
```Shell
jake runtests-parallel
```
This run will all tests; to run only a specific subset of tests, use:
```Shell
jake runtests tests=<regex>
```
e.g. to run all compiler baseline tests:
```Shell
jake runtests tests=compiler
```
or to run a specific test: `tests\cases\compiler\2dArrays.ts`
```Shell
jake runtests tests=2dArrays
```
## Debugging the tests
To debug the tests, invoke the `runtests-browser` task from jake.
You will probably only want to debug one test at a time:
```Shell
jake runtests-browser tests=2dArrays
```
You can specify which browser to use for debugging. Currently Chrome and IE are supported:
You can debug with VS Code or Node instead with `jake runtests debug=true`:
```Shell
jake runtests tests=2dArrays debug=true
```
## Adding a Test
To add a new test case, simply place a `.ts` file in `tests\cases\compiler` containing code that exemplifies the bugfix or change you are making.
These files support metadata tags in the format `// @metaDataName: value`.
The supported names and values are the same as those supported in the compiler itself, with the addition of the `fileName` flag.
`fileName` tags delimit sections of a file to be used as separate compilation units.
They are useful for tests relating to modules.
See below for examples.
**Note** that if you have a test corresponding to a specific spec compliance item, you can place it in `tests\cases\conformance` in an appropriately-named subfolder.
**Note** that filenames here must be distinct from all other compiler testcase names, so you may have to work a bit to find a unique name if it's something common.
### Tests for multiple files
When one needs to test for scenarios which require multiple files, it is useful to use the `fileName` metadata tag as such:
```TypeScript
// @fileName: file1.ts
export function f() {
}
// @fileName: file2.ts
import { f as g } from "file1";
var x = g();
```
One can also write a project test, but it is slightly more involved.
## Managing the Baselines
Compiler testcases generate baselines that track the emitted `.js`, the errors produced by the compiler, and the type of each expression in the file. Additionally, some testcases opt in to baselining the source map output.
When a change in the baselines is detected, the test will fail. To inspect changes vs the expected baselines, use
```Shell
jake diff
```
After verifying that the changes in the baselines are correct, run
```Shell
jake baseline-accept
```
to establish the new baselines as the desired behavior. This will change the files in `tests\baselines\reference`, which should be included as part of your commit. It's important to carefully validate changes in the baselines.
**Note** that `baseline-accept` should only be run after a full test run! Accepting baselines after running a subset of tests will delete baseline files for the tests that didn't run.
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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5. Submission of Contributions. Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions. Notwithstanding the above, nothing herein shall supersede or modify the terms of any separate license agreement you may have executed with Licensor regarding such Contributions.
6. Trademarks. This License does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor, except as required for reasonable and customary use in describing the origin of the Work and reproducing the content of the NOTICE file.
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8. Limitation of Liability. In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall any Contributor be liable to You for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising as a result of this License or out of the use or inability to use the Work (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if such Contributor has been advised of the possibility of such damages.
9. Accepting Warranty or Additional Liability. While redistributing the Work or Derivative Works thereof, You may choose to offer, and charge a fee for, acceptance of support, warranty, indemnity, or other liability obligations and/or rights consistent with this License. However, in accepting such obligations, You may act only on Your own behalf and on Your sole responsibility, not on behalf of any other Contributor, and only if You agree to indemnify, defend, and hold each Contributor harmless for any liability incurred by, or claims asserted against, such Contributor by reason of your accepting any such warranty or additional liability.
[](https://gitter.im/Microsoft/TypeScript?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
[TypeScript](http://www.typescriptlang.org/) is a language for application-scale JavaScript. TypeScript adds optional types, classes, and modules to JavaScript. TypeScript supports 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](http://www.typescriptlang.org/Playground), and stay up to date via [our blog](https://blogs.msdn.microsoft.com/typescript) and [Twitter account](https://twitter.com/typescriptlang).
## Installing
For the latest stable version:
```
npm install -g typescript
```
For our nightly builds:
```
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](http://stackoverflow.com/questions/tagged/typescript).
* Join the [#typescript](http://twitter.com/#!/search/realtime/%23typescript) discussion on Twitter.
* 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 file is based on or incorporates material from the projects listed below (collectively "Third Party Code"). Microsoft is not the original author of the Third Party Code. The original copyright notice and the license, under which Microsoft received such Third Party Code, are set forth below. Such licenses and notices are provided for informational purposes only. Microsoft, not the third party, licenses the Third Party Code to you under the terms set forth in the EULA for the Microsoft Product. Microsoft reserves all other rights not expressly granted under this agreement, whether by implication, estoppel or otherwise.
DefinitelyTyped
This project is licensed under the MIT license.
Copyrights are respective of each contributor listed at the beginning of each definition file.
Provided for Informational Purposes Only
MIT License
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ""Software""), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
