Documentation: usage of types/interfaces defined in modules on global

Search Terms

• export from module to global
• global namespace
• declare as global
• assign to global
• globalThis

Suggestion

Documentation says that

It can be surprisingly difficult to access or declare values in the global scope, perhaps because we’re writing our code in modules...

(https://devblogs.microsoft.com/typescript/announcing-typescript-3-4/#type-checking-for-globalthis)

It shows an example how typed variable may be declared in the global scope. But it doesn't cover scenario when one needs to declare variable/function/namespace which use a type/interface declared in some module.

I think that the documentation should clearly explain that it's not possible or show an example how to do it (if it's possible).

Use Case

One creates a function with input parameter and/or return type declared in module.
She wants to make this function available on global.

It's an anti-pattern in the same way as augmenting types from external modules, but as discussed here #5292 it exists in real life.

One may have a well organised non-poluting-global modules-based codebase. But at some point by some reason she have to provide an interface for a global consumer. Moving all exposed interfaces and types to global and rewrite the codebase which used to consume them from modules would be ugly and painful.

Example

import { SomeType, SomeInterface } from 'some/module';

function functionForGlobalConsumer(input: SomeType): SomeInterface {
  // some code...
}

globalThis.functionForGlobalConsumer = functionForGlobalConsumer;

Checklist

My suggestion meets these guidelines:

• 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, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Beginne mit dem im Issue verlinkten Dokumentationsbeispiel zu TypeScript 3.4 globalThis und reproduziere das gezeigte Szenario mit einem importierten Typ. Ermittle, ob die Dokumentation ein unterstütztes Muster oder eine Einschränkung beschreiben sollte, aktualisiere dann die relevanten Hinweise zum globalen Gültigkeitsbereich mit einem klaren Beispiel oder einer Erklärung und überprüfe, dass damit der angegebene Anwendungsfall abgedeckt wird.