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TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
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ahejlsberg Merge pull request #32460 from microsoft/fix32434
Improve type inference for types like 'T | Promise<T>'
Latest commit 9ec71c3 Jul 23, 2019
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.github Update Apr 25, 2019
.vscode Migrate tscWatchMode to vfs Nov 22, 2017
bin Moved LKG folder to lib Jul 27, 2015
doc fix spelling errors Jan 28, 2019
lib Rename _objectLiteralBrandBrand to _objectLiteralBrand. (#30797) Apr 23, 2019
scripts Add support for sharding tests across multiple workers (#32173) Jul 1, 2019
src Merge pull request #32460 from microsoft/fix32434 Jul 23, 2019
tests Merge pull request #32460 from microsoft/fix32434 Jul 23, 2019
.dockerignore Add dockerfile based tests for `azure-sdk-for-js` and `office-ui-fabr… Jun 20, 2019
.editorconfig Use CRLF, not LF. Mar 2, 2015
.gitattributes Never normalize end-of-lines on clone/commit. May 31, 2015
.gitignore Add xterm test to docker suite (#32149) Jun 27, 2019
.gitmodules Add prettier user test and fix associated crash (#23715) Apr 26, 2018
.mailmap Update .mailmap Oct 27, 2018
.npmignore Add dockerfile based tests for `azure-sdk-for-js` and `office-ui-fabr… Jun 20, 2019
.npmrc Remove lockfile, add to gitignore, and add npmrc preventing its gener… Aug 17, 2018
.travis.yml remove sudo: false setting from travis.yml (#30231) Mar 5, 2019
.yarnrc Adds a yarnrc which makes sure that the lockfile isn't generated for … Jun 12, 2019 Update authors for release 3.0 Jul 11, 2018 Added Microsoft code of conduct file Oct 5, 2018 Update docs to reflect the removal of the "Community" milestone. Apr 22, 2019
CopyrightNotice.txt Baseline public API (#18897) Oct 3, 2017
Dockerfile Add dockerfile based tests for `azure-sdk-for-js` and `office-ui-fabr… Jun 20, 2019
Gulpfile.js Add support for sharding tests across multiple workers (#32173) Jul 1, 2019
LICENSE.txt Add snapshot of compiler sources Jul 13, 2014 Moved the badges below the Typescript Header May 12, 2019
ThirdPartyNoticeText.txt Update ThirdPartyNoticeText to include KhronosGroup copyright notice … Jul 31, 2018
package.json Skip costly tests Jun 14, 2019
tslint.json Exclude everything in tests Apr 24, 2019


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TypeScript 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, and stay up to date via our blog and Twitter account.


For the latest stable version:

npm install -g typescript

For our nightly builds:

npm install -g typescript@next


There are many ways to contribute to TypeScript.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.



In order to build the TypeScript compiler, ensure that you have Git and Node.js installed.

Clone a copy of the repo:

git clone

Change to the TypeScript directory:

cd TypeScript

Install Gulp tools and dev dependencies:

npm install -g gulp
npm install

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.
                      # You can override the host or specify a test for this command.
                      # Use --host=<hostName> or --tests=<testPath>.
gulp baseline-accept  # This replaces the baseline test results with the results obtained from gulp runtests.
gulp lint             # Runs tslint on the TypeScript source.
gulp help             # List the above commands.


node built/local/tsc.js hello.ts


For details on our planned features and future direction please refer to our roadmap.

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