CODEWITHSUNDEEP
typescriptglobal-variablesdeno
Tibor Huđik
Tibor Huđik

Reputation: 55

How to define global variable in Deno?

I am new to Deno and TypeScript but have plenty of experience using NodeJs and Javascript, I have stumbled on an issue of sorts, that I could have easily sorted out in NodeJs by simply adding global into the mix, however, that shows to be rather difficult in Deno for some reason.

I want to declare the First variable that should be available globally everywhere without need to import it. (sort of like Deno variable is available)

Here is an example of the code I'm trying to get running:

/// index.ts
import { FirstClass } from './FirstClass.ts';

global.First = new FirstClass();

await First.commit();


/// FirstClass.ts
import { SecondClass } from './SecondClass.ts';
export class FirstClass {
  constructor() {}
  async commit() {
    const second = new SecondClass();

    await second.comment();
  }
}


/// SecondClass.ts
export class SecondClass {
  constructor() {}
  comment() {
    console.log(First); // Should log the FirstClass
  }
}

I would run this code like this: deno run index.ts

Upvotes: 5

Views: 6290

Answers (2)

SebastienGllmt
SebastienGllmt

Reputation: 86

If you were doing this to try and add in a Node.js global variable to Deno, you'll be glad to hear that in Deno 2.1 they added a new --unstable-node-globals option to add in the nodejs globals automatically for you.

This will fix the runtime behavior, but you will still need to convince TypeScript this variable exists (it can't infer this from the command line in Deno 2.1), so you can fix this by adding the following code in your project:

declare global {
  type Buffer = typeof import("node:buffer").Buffer;
}

Upvotes: 0

Marcos Casagrande
Marcos Casagrande

Reputation: 40444

The global object in Deno is: window / globalThis

window.First = new FirstClass();

For TypeScript compiler errors see: How do you explicitly set a new property on `window` in TypeScript?

declare global {
    var First: FirstClass
    interface Window { First: any; }
}

window.First = new FirstClass();
await First.commit();

Upvotes: 7

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