Proposal: GlobalConstructor

[remcohaszing]

Sometimes it’s useful to get a property which may or may not exist on a type.

A practical example is that many libraries support both NodeJS buffers and a browser environment. If these libraries depend on the Buffer type, they need to pull in @types/node. However, this is undesirable for a browser environment. This helper type could resolve the issue like this:

// This is the same as `Buffer` in a Node environment, but `never` in a browser environment.
type Buffer = GlobalConstructor<'Buffer'>

[sindresorhus]

What does the code for GlobalConstructor look like? It's hard to evaluate the proposal without seeing how it might work.

[remcohaszing]

I’m not sure what it should look like. I can think of specific implementations, but not of a reusable one as I proposed here.

Perhaps it’s better to just expose some types with quirky behaviour between NodeJS and the dom lib.

// Buffer if @types/node is included
// never if @types/node is not included
export type Buffer = typeof globalThis extends {Buffer: {from: (string: any) => infer T}} ? T : never

Unfortunately if this is processed by TypeScript when generating a .d.ts file from a .ts file, it’s normalized to either Buffer or never.

[voxpelli]

Currently this module has no types which interacts with the global types in any way.

The README points to https://github.com/g-plane/typed-query-selector for document.querySelector and document.querySelectorAll

I think this is best handled in a similar way, keeping this module's focus strictly on utility types in the spirit of https://www.typescriptlang.org/docs/handbook/utility-types.html

[sindresorhus]

I agree with @voxpelli. I also think it's a problem the TypeScript project should fix. I would recommend opening an issue there about it: https://github.com/microsoft/TypeScript