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In TypeScript, say I want to have the user use my module's "internal" types so they can properly type their own variables when using my module - do I just export literally everything from my index.ts file to accomplish this?

// index.ts

export * from './file1' // uses types/interfaces defined in file1types
export * from './file2' // uses types/interfaces defined in file2types
export * from './types/file1types'
export * from './types/file2types'

Do .d.ts files help me accomplish this, or are they only for non-TS projects? Does tsconfig.json's option declaration: true help me accomplish this by generating a .d.ts for every TS file? Is this an alternative to exporting everything from a single index.ts file?

And if declaration: true does help me accomplish this, how would the user use all those generated .d.ts files within the build folder?

I would greatly appreciate some clarification as to how one typically exports types in TS projects. Thanks in advance.

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  • I'm not sure I understand the question, if you want to export a type for users of your API to use, just export it... Commented Mar 16, 2020 at 19:50
  • 1
    In your package.json file you need to provide the location of the .d.ts entry file { "types": "types/index.d.ts" } also in your typescript file "declaration": true and "declarationDir": "./types" Commented Mar 16, 2020 at 21:00

2 Answers 2

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25

Without declaration files you can develop a package in TypeScript, compile it and expose it to other users as JavaScript code. Including them also allows TypeScript developers to use the package with any types you defined in it. They can get more type information whilst working with your library, such as required arguments types, function return types etc, as well as warnings from their IDE/Intellisense when there are conflicts.

The declaration: true in the file tsconfig.json instructs the TypeScript compiler to output declaration files (.d.ts). Often they are bundled in a single file e.g. index.d.ts and then a "types": path/to/index.d.ts field is added to the library's package.json file to inform TypeScript where to look for the types (when a user imports the package).

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21

For those who are like me, and have made sure declaration: true is set in your tsconfig.json, and that your build process correctly creates the corresponding .d.ts files to the appropriate directory pointed to by your package.json file, AND STILL somehow can't access the internal types of your module when testing on an external project -- try restarting the TS server in VSCode (assuming you're using VSCode)

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So much time was wasted trying to figure this out, only to realize Typescript was functioning fine and I was being sabotaged by my IDE.

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5 Comments

I can't believe this worked...
The same for WebStorm, BTW. I regularily restart Typescript to see it functioning the way it should.
@YoavMoran, thanks for the tip. I now see there's a "Restart TypeScript Service" command in Webstorm. I'd just been restarting the whole IDE when TS acted up.
Tip: bottom right of screen on the status bar of Webstorm, click on TypeScript 4.X.X and restart from there
The error appeared randomly after enums working for a couple of commits and it went away using this approach.

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