DefinitelyTyped

The repository for high quality TypeScript type definitions.

Also see the definitelytyped.org website, although information in this README is more up-to-date.

You can also read this README in Spanish and Korean!

What are declaration files?

See the TypeScript handbook.

How do I get them?

npm

This is the preferred method. This is only available for TypeScript 2.0+ users. For example:

npm install --save-dev @types/node

The types should then be automatically included by the compiler. See more in the handbook.

For an NPM package "foo", typings for it will be at "@types/foo". If you can't find your package, look for it on TypeSearch.

If you still can't find it, check if it bundles its own typings. This is usually provided in a "types" or "typings" field in the package.json, or just look for any ".d.ts" files in the package and manually include them with a /// <reference path="" />.

Other methods

These can be used by TypeScript 1.0.

• Typings
• NuGet (use preferred alternatives, nuget DT type publishing has been turned off)
• Manually download from the master branch of this repository

You may need to add manual references.

How can I contribute?

DefinitelyTyped only works because of contributions by users like you!

Test

Before you share your improvement with the world, use it yourself.

Test editing an existing package

To add new features you can use module augmentation. You can also directly edit the types in node_modules/@types/foo/index.d.ts, or copy them from there and follow the steps below.

Test a new package

Add to your tsconfig.json:

"baseUrl": "types",
"typeRoots": ["types"],

(You can also use src/types.) Create types/foo/index.d.ts containing declarations for the module "foo". You should now be able import from "foo" in your code and it will route to the new type definition. Then build and run the code to make sure your type definition actually corresponds to what happens at runtime. Once you've tested your definitions with real code, make a PR then follow the instructions to edit an existing package or create a new package.

Make a pull request

Once you've tested your package, you can share it on DefinitelyTyped.

First, fork this repository, install node, and run npm install.

Edit an existing package

• cd types/my-package-to-edit
• Make changes. Remember to edit tests. If you make breaking changes, do not forget to update a major version.
• You may also want to add yourself to "Definitions by" section of the package header.
  • This will cause you to be notified (via your GitHub username) whenever someone makes a pull request or issue about the package.
  • Do this by adding your name to the end of the line, as in // Definitions by: Alice <https://github.com/alice>, Bob <https://github.com/bob>.
  • Or if there are more people, it can be multiline

  // Definitions by: Alice <https://github.com/alice>
  //                 Bob <https://github.com/bob>
  //                 Steve <https://github.com/steve>
  //                 John <https://github.com/john>

• If there is a tslint.json, run npm run lint package-name. Otherwise, run tsc in the package directory.

When you make a PR to edit an existing package, dt-bot should @-mention previous authors. If it doesn't, you can do so yourself in the comment associated with the PR.

Create a new package

If you are the library author and your package is written in TypeScript, bundle the autogenerated declaration files in your package instead of publishing to DefinitelyTyped.

If you are adding typings for an NPM package, create a directory with the same name. If the package you are adding typings for is not on NPM, make sure the name you choose for it does not conflict with the name of a package on NPM. (You can use npm info foo to check for the existence of the foo package.)

Your package should have this structure:

File	Purpose
index.d.ts	This contains the typings for the package.
foo-tests.ts	This contains sample code which tests the typings. This code does not run, but it is type-checked.
tsconfig.json	This allows you to run tsc within the package.
tslint.json	Enables linting.

Generate these by running npx dts-gen --dt --name my-package-name --template module if you have npm ≥ 5.2.0, npm install -g dts-gen and dts-gen --dt --name my-package-name --template module otherwise. See all options at dts-gen.

You may edit the tsconfig.json to add new files, to add "target": "es6" (needed for async functions), to add to "lib", or to add the "jsx" compiler option.

DefinitelyTyped members routinely monitor for new PRs, though keep in mind that the number of other PRs may slow things down.

For a good example package, see base64-js.

Common mistakes

• First, follow advice from the handbook.
• Formatting: Either use all tabs, or always use 4 spaces.
• function sum(nums: number[]): number: Use ReadonlyArray if a function does not write to its parameters.
• interface Foo { new(): Foo; }: This defines a type of objects that are new-able. You probably want declare class Foo { constructor(); }.
• const Class: { new(): IClass; }: Prefer to use a class declaration class Class { constructor(); } instead of a new-able constant.
• getMeAT<T>(): T: If a type parameter does not appear in the types of any parameters, you don't really have a generic function, you just have a disguised type assertion. Prefer to use a real type assertion, e.g. getMeAT() as number. Example where a type parameter is acceptable: function id<T>(value: T): T;. Example where it is not acceptable: function parseJson<T>(json: string): T;. Exception: new Map<string, number>() is OK.
• Using the types Function and Object is almost never a good idea. In 99% of cases it's possible to specify a more specific type. Examples are (x: number) => number for functions and { x: number, y: number } for objects. If there is no certainty at all about the type, any is the right choice, not Object. If the only known fact about the type is that it's some object, use the type object, not Object or { [key: string]: any }.
• var foo: string | any: When any is used in a union type, the resulting type is still any. So while the string portion of this type annotation may look useful, it in fact offers no additional typechecking over simply using any. Depending on the intention, acceptable alternatives could be any, string, or string | object.

Removing a package

When a package bundles its own types, types should be removed from DefinitelyTyped to avoid confusion.

You can remove it by running npm run not-needed -- typingsPackageName asOfVersion sourceRepoURL [libraryName].

• typingsPackageName: This is the name of the directory to delete.
• asOfVersion: A stub will be published to @types/foo with this version. Should be higher than any currently published version.
• sourceRepoURL: This should point to the repository that contains the typings.
• libraryName: Descriptive name of the library, e.g. "Angular 2" instead of "angular2". (If ommitted, will be identical to "typingsPackageName".)

Any other packages in DefinitelyTyped that referenced the deleted package should be updated to reference the bundled types. To do this, add a package.json with "dependencies": { "foo": "x.y.z" }.

If a package was never on DefinitelyTyped, it does not need to be added to notNeededPackages.json.

Lint

All new packages must be linted. To lint a package, add a tslint.json to that package containing

{ 
    "extends": "dtslint/dt.json" 
}

This should be the only content in a finished project's tslint.json file. If a tslint.json turns rules off, this is because that hasn't been fixed yet. For example:

{
    "extends": "dtslint/dt.json",
    "rules": {
        // This package uses the Function type, and it will take effort to fix.
        "ban-types": false
    }
}

(To indicate that a lint rule truly does not apply, use // tslint:disable rule-name or better, //tslint:disable-next-line rule-name.)

To assert that an expression is of a given type, use $ExpectType. To assert that an expression causes a compile error, use $ExpectError.

// $ExpectType void
f(1);

// $ExpectError
f("one");

For more details, see dtslint readme.

Test by running npm run lint package-name where package-name is the name of your package. This script uses dtslint.

FAQ

What exactly is the relationship between this repository and the @types packages on NPM?

The master branch is automatically published to the @types scope on NPM thanks to types-publisher.

I've submitted a pull request. How long until it is merged?

It depends, but most pull requests will be merged within a week. PRs that have been approved by an author listed in the definition's header are usually merged more quickly; PRs for new definitions will take more time as they require more review from maintainers. Each PR is reviewed by a TypeScript or DefinitelyTyped team member before being merged, so please be patient as human factors may cause delays. Check the PR Burndown Board to see progress as maintainers work through the open PRs.

My PR is merged; when will the @types NPM package be updated?

NPM packages should update within a few hours. If it's been more than 24 hours, ping @RyanCavanaugh and @andy-ms on the PR to investigate.

I'm writing a definition that depends on another definition. Should I use <reference types="" /> or an import?

If the module you're referencing is an external module (uses export), use an import. If the module you're referencing is an ambient module (uses declare module, or just declares globals), use <reference types="" />.

I notice some packages having a package.json here.

Usually you won't need this. When publishing a package we will normally automatically create a package.json for it. A package.json may be included for the sake of specifying dependencies. Here's an example. We do not allow other fields, such as "description", to be defined manually. Also, if you need to reference an older version of typings, you must do that by adding "dependencies": { "@types/foo": "x.y.z" } to the package.json.

Some packages have no tslint.json, and some tsconfig.json are missing "noImplicitAny": true, "noImplicitThis": true, or "strictNullChecks": true.

Then they are wrong. You can help by submitting a pull request to fix them.

Can I request a definition?

Here are the currently requested definitions.

What about type definitions for the DOM?

If types are part of a web standard, they should be contributed to TSJS-lib-generator so that they can become part of the default lib.dom.d.ts.

A package uses export =, but I prefer to use default imports. Can I change export = to export default?

If you are using TypeScript 2.7 or later, use --esModuleInterop in your project. Otherwise, if default imports work in your environment (e.g. Webpack, SystemJS, esm), consider turning on the --allowSyntheticDefaultImports compiler option. Do not change the type definition if it is accurate. For an NPM package, export = is accurate if node -p 'require("foo")' is the export, and export default is accurate if node -p 'require("foo").default' is the export.

I want to use features from TypeScript 2.1 or above.

Then you will have to add a comment to the last line of your definition header (after // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped): // TypeScript Version: 2.1.

I want to add a DOM API not present in TypeScript by default.

This may belong in TSJS-Lib-Generator. See the guidelines there. If the standard is still a draft, it belongs here. Use a name beginning with dom- and include a link to the standard as the "Project" link in the header. When it graduates draft mode, we may remove it from DefinitelyTyped and deprecate the associated @types package.

I want to update a package to a new major version

If you intend to continue updating the older version of the package, you may create a new subfolder with the current version e.g. v2, and copy existing files to it. If so, you will need to:

1. Update the relative paths in tsconfig.json as well as tslint.json.
2. Add path mapping rules to ensure that tests are running against the intended version.

For example history v2 tsconfig.json looks like:

{
    "compilerOptions": {
        "baseUrl": "../../",
        "typeRoots": ["../../"],
        "paths": {
            "history": [ "history/v2" ]
        },
    },
    "files": [
        "index.d.ts",
        "history-tests.ts"
    ]
}

If there are other packages on DefinitelyTyped that are incompatible with the new version, you will need to add path mappings to the old version. You will also need to do this for packages depending on packages depending on the old version.

For example, react-router depends on history@2, so react-router tsconfig.json has a path mapping to "history": [ "history/v2" ]; transitively react-router-bootstrap (which depends on react-router) also adds a path mapping in its tsconfig.json.

Also, /// <reference types=".." /> will not work with path mapping, so dependencies must use import.

How do I write definitions for packages that can be used globally and as a module?

The TypeScript handbook contains excellent general information about writing definitions, and also this example definition file which shows how to create a definition using ES6-style module syntax, while also specifying objects made available to the global scope. This technique is demonstrated practically in the definition for big.js, which is a library that can be loaded globally via script tag on a web page, or imported via require or ES6-style imports.

To test how your definition can be used both when referenced globally or as an imported module, create a test folder, and place two test files in there. Name one YourLibraryName-global.test.ts and the other YourLibraryName-module.test.ts. The global test file should exercise the definition according to how it would be used in a script loaded on a web page where the library is available on the global scope - in this scenario you should not specify an import statement. The module test file should exercise the definition according to how it would be used when imported (including the import statement(s)). If you specify a files property in your tsconfig.json file, be sure to include both test files. A practical example of this is also available on the big.js definition.

Please note that it is not required to fully exercise the definition in each test file - it is sufficient to test only the globally-accessible elements on the global test file and fully exercise the definition in the module test file, or vice versa.

What about scoped packages?

Types for a scoped package @foo/bar should go in types/foo__bar. Note the double underscore.

When dts-gen is used to scaffold a scoped package, the paths property has to be manually adapted in the generated tsconfig.json to correctly reference the scoped package:

{
    "paths":{
      "@foo/bar": ["foo__bar"]
    }
}

The file history in GitHub looks incomplete.

GitHub doesn't support file history for renamed files. Use git log --follow instead.

Should I add an empty namespace to a package that doesn't export a module to use ES6 style imports?

Some packages, like chai-http, export a function.

Importing this module with an ES6 style import in the form import * as foo from "foo"; leads to the error:

error TS2497: Module 'foo' resolves to a non-module entity and cannot be imported using this construct

This error can be suppressed by merging the function declaration with an empty namespace of the same name, but this practice is discouraged. This is a commonly cited Stack Overflow answer regarding this matter.

It is more appropriate to import the module using the import foo = require("foo"); syntax, or to use a default import like import foo from "foo"; if using the --allowSyntheticDefaultImports flag if your module runtime supports an interop scheme for non-ECMAScript modules as such.

License

This project is licensed under the MIT license.

Copyrights on the definition files are respective of each contributor listed at the beginning of each definition file.

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