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* Switch index signature storage to 'indexInfos: IndexInfo[]' property * Accept new baselines * Remove another usage of IndexKind enum * Update getIndexedAccessType and resolveMappedTypeMembers * Accept new baselines * Update grammar checking for index signatures * Accept new baselines * Consider all index signatures in mapped types and union types * Accept new baselines * Update getIndexType * Accept new baselines * Intersect multiple applicable index signatures * Use getApplicableIndexInfo instead of hardwired string/number handling * Update index signature relationship checking * Report type for which index signature is missing * Report type for which index signature is missing * Accept new baselines * Make 'number' index signatures consistently apply to numeric strings * Accept new baselines * Update fourslash test * Revise index constraint checking * Accept new baselines * Update error messages * Accept new baselines * Update type inference from index signatures * Update isKnownProperty * Update contextual typing based on index signatures * Accept new baselines * Support union types in index signature declarations * Accept new baselines * Check duplicate index signatures / remove redundant template literals from unions with string * Accept new baselines * Include key type in diagnostic / check symbol-named properties * Accept new baselines * Minor fix * Add tests * Accept new baselines * Add optimized findApplicableIndexInfoForName * Accept new baselines * Another place we don't need to obtain literal type for property name * Accept new baselines * Don't create literal types that are going to be discarded * Individual maps for string, number, bigint, and enum literal types * Remove ineffective optimizations * Accept new baselines * Permit intersections as key types in index signatures * Index expression in element access is template literal context * Add tests * Accept new baselines * Symbol index signatures from object literals with computed symbol properties * Accept new baselines * Add more tests * Accept new baselines * Implement Go To Definition for all applicable index signatures * Add fourslash test * Accept new API baselines
TypeScript
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.
Find others who are using TypeScript at our community page.
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 to TypeScript.
- Submit bugs and help us verify fixes as they are checked in.
- Review the source code changes.
- Engage with other TypeScript users and developers on StackOverflow.
- Help each other in the TypeScript Community Discord.
- Join the #typescript discussion on Twitter.
- Contribute bug fixes.
- Read the archived language specification (docx, pdf, md).
This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
Documentation
Building
In order to build the TypeScript compiler, ensure that you have Git and Node.js installed.
Clone a copy of the repo:
git clone https://github.com/microsoft/TypeScript.git
Change to the TypeScript directory:
cd TypeScript
Install Gulp tools and dev dependencies:
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.
# 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
node built/local/tsc.js hello.ts
Roadmap
For details on our planned features and future direction please refer to our roadmap.