How to add custom "typings" in typescript 2.0 / 3.0

Question

According to this article typings system for typescript 2.0 has changed and so it is not clear how to attach custom typings now. Should I always create NPM package for that?

Thank you in advance!

Answer 1

You can create local custom typings just for your project, where you can declare types for JS libraries. For that, you need to:

1. Create directory structure to keep your type declaration files so that your directory structure looks similar to this:

    .  ├── custom_typings  │   └── some-js-lib  │       └── index.d.ts  └── tsconfig.json 

2. In the index.d.ts file, add a declaration for your JS library:

    declare module 'some-js-lib' {    export function hello(world: string): void  } 

3. (Optional: skip if you have TypeScript >= 4.x) Add a reference to this type declaration in the compilerOptions section of your tsconfig.json:

    {    "compilerOptions": {      ...      "typeRoots": ["./node_modules/@types", "./custom_typings"]    },    ...  } 

4. Use the declared module in your code:

    import { hello } from 'some-js-lib'   hello('world!')