Create a global function like jest does

Question

I am working on a meta framework that will use react.

I would like to offer some functions that are directly available without the need of an import, exactly like jest does with the function it(), beforeAll() etc...

I basically succeed by simply declaring a typed var like this :

//myfile.d.ts
declare var someFunction : () =>  string

and then by assigning a function to it :

//someFile.ts
someFunction = () => "This is working"

Then, at the root of the project, I just imported once someFile.ts to make sure that someFunction was defined :

import "./someFile"

and yep, we are good, the function is global and does not require an import, and correctly typed !

So , what is the problem ?

Well this work when I declare my type myself. But if I need to use a library's type to create my own type, it does not work anymore

Let say I want to make the axios object available globally without the need to have an import.

So here is what I did in the declaration file

import { Axios } from "axios"
interface MyOwnAxiosType extends Axios {}

declare var myOwnAxios:MyOwnAxiosType

But as soon as the import is added at the top, the myOwnAxios is not found anymore outside of this file

If you have any idea of what I may be doing wrong, any help would be appreciated, thanks !

Answer 1

Here is the solution: In a ts file

import * as axios_ from "axios"

declare global {
    var myOwnAxioss : typeof axios_.default
}
global.myOwnAxioss = axios_ as any

And that's it, you can now do this without any import, and with typings.

myOwnAxioss.get()

Answer 2

Using import in your file makes your declaration file a module and not an ambient declaration context.

Instead you will have to use this confusing syntax:

import Axios = import("axios").Axios;

interface MyOwnAxiosType extends Axios {}

declare var myOwnAxios:MyOwnAxiosType

• import("axios") imports the module axios as a namespace (only types)

• import("axios").Axios gets the type Axios from the namespace

• import Axios = import("axios").Axios give the type above an alias

Using this kind of import will solve the issue because you are no longer using a static import.

---

If that doesn't work you can try inlining it:

interface MyOwnAxiosType extends import("axios").Axios {}

declare var myOwnAxios:MyOwnAxiosType