Assign existing interface to global (globalThis)

🔍 Search Terms

• global
• globalThis
• window

✅ Viability Checklist

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

Currently, to provide types to globalThis, I can update the global.d.ts similar to:

declare global {
    interface Navigator {
        ...
    }
}

However, if I want to set the interface of the global object (e.g. to give it the an interface that extends theWindow interface, I'd have to do something like this at the top of each .ts file that references globalThis like the below:

interface MyWindow extends Window {}

declare let globalThis: MyWindow;

I'd like to see a way where I can modify the whole interface of the global object.

📃 Motivating Example

Override the whole ` interface.

💻 Use Cases

Working across multiple runtimes which share the same global interface without having a large global.d.ts with copy/pasted interfaces from utility types.

Start by reviewing the global.d.ts and declare global examples in the issue, along with the proposed globalThis declaration. Determine how an interface for the whole global object should be modified across multiple runtimes, and define completion as a supported, non-breaking declaration approach with its behavior covered by appropriate tests.