window.parent should have the same global variables as window

[lukejagodzinski]

TypeScript Version: 4.1.2

Search Terms: window.parent, window.Element, globalThis

Code

window.HTMLDivElement;
window.parent.HTMLDivElement; // Error here

Expected behavior:

The window.parent object should have the same base global variables as the window object. If not in the context of iframe, then window === window.parent so all global variables should be the same in such a case. When being in the iframe context window !== window.parent however it should still have all the base global variables, so that we can do for example element instanceof window.parent.Element. You could think, why don't just write element instanceof Element? The answer is that it would work in almost all browsers beside Chrome. And Chrome is actually the one implementing it correctly. Both global window and iframe window have their own global context so window.parent.Element !== window.Element. In TS all the global variables are defined in the globalThis so the type for the window.parent should be declare var parent: Window & typeof globalThis;

Actual behavior:

The window.parent.HTMLDivElement; does not exist on type Window.

Playground Link: https://www.typescriptlang.org/play?#code/O4SwdgJg9sB0ASAVAsgGQCIgG4FEA2ApgLYFgAuA3AFCiQywAOAhgE6lkIobb7HsVA

[andrewbranch]

The problem is that then you go too far in the opposite direction; globalThis can easily contain things that wouldn’t be shared between an iframe and its parent. Suppose this script ran in an iframe?

[lukejagodzinski]

I see your point. My solution was just a quick guess just by looking how the window object is typed. I didn't know how the globalThis works. My point is just that window.parent should have all the base global variables. Maybe the solution would be to define them in some interface and extend it by both window and window.parent. Or maybe actually put them in the Window interface?

[HolgerJeromin]

Same with UIEvent.prototype.view

For Document.defaultView we had this PR which has the same problem as @andrewbranch wrote:
microsoft/TypeScript-DOM-lib-generator#820 (added & typeof globalThis)

[eps1lon]

For Document.defaultView we had this PR which has the same problem as @andrewbranch wrote:
microsoft/TypeScript-DOM-lib-generator#820 (added & typeof globalThis)

Yeah I see now how this overshot. But defaultView not having HTMLInputElement was also annoying.