Typescript: declare a type in .d.ts file and use it without importing

Question

I want to know what is the right way to use types or interfaces without directly importing them (if that's an ok idea).

Currently I have this code:

import { TCollection } from "../__types__"; function doSomething(collection: TCollection) { // ... }

So to get rid of an import statement I have tried to replace typeRoots inside of tsconfig.json with this value:

{ "compilerOptions": { ... "typeRoots": ["./src/__types__/types.d.ts", "./node_modules/@types"], } }

And declared a type in ./src/__types__/types.d.ts:

declare type TCollection = { ... };

But still having an error:

function doSomething(collection: TCollection) { ^^^^^^^^^^^ Cannot find name 'TCollection'.ts(2304) }

Did I made a mistake or is it an IDE bug or something? Thanks

Does it work, if you change your typeroots to: "typeRoots": ["./src/__types__", "./node_modules/@types"],? — Ali Nasserzadeh
– Ali Nasserzadeh, Commented Apr 14, 2020 at 14:41

DoronG · Accepted Answer · 2024-04-17 14:36:33Z

you can define the types on the global scope:

// global-types.d.ts import { Something } from "somewhere"; declare global { interface TCollection { ... } }

if you do not need to import anything in your global-types.d.ts you can just declare the interface directly:

// global-types.d.ts interface TCollection { ... }

no need for any tsconfig changes

1 Answer 1