Node.js Global Variable And TypeScript

I need to have some strongly-typed global variables. As mentioned here: Extending TypeScript Global object in node.js, in order to add fields to the global variable I need to add a

Solution 1:

Here's an approach. I don't know if this is the 'correct' way of doing things, but it works for me with TypeScript 3.7.4.

1. Assuming your source files live in a folder src, create a new folder src/types and create a file global.d.ts in this folder.
2. Author your declarations using one of the following strategies:
   • If you need to import external types into your declaration file, use the following syntax:

import { Express } from 'express';

declare global {
  namespace NodeJS {
    interface Global {
      __EXPRESS_APP__: Express;
    }
  }
}

• If your declaration file does not contain any imports, the above will not work, and you'll need to use this syntax instead:

declare namespace NodeJS {
  interface Global {
    __CONNECTION_COUNT__: number;
  }
}

4. Make sure your global.d.ts file (and any other files you might add to src/types) is picked up by the TypeScript compiler, by adding the following to your tsconfig.json file:

{
  "paths": {
    "*": ["node_modules/*", "src/types/*"]
  }
}

5. Use the global variable as normal inside your code.

// Below, `app` will have the correct typings
const app = global.__EXPRESS_APP__;

Solution 2:

I found this works.

Have one file that declares the property on the NodeJS.Global interface with the any type. This file has to be clean of imports or refrences.

node.d.ts

declare namespace NodeJS{
    interface Global {
        foo: any
    }
}

Then in the second file you declare a global variable that has the correct type.

global.d.ts

import IFoo from '../foo'

declare global {

  const foo:Ifoo

}