Why is Object overwritten?

[tylersayshi]

from this code: https://github.com/sinclairzx81/typebox/blob/master/src/type/object/object.ts#L94-L101

by using var here, the runtime Object class is being overwritten. I'm curious if this is done intentionally. If it is intentional, is the code extending the default Object or replacing it fully?

Thanks!

[sinclairzx81]

@tylersayshi Hi,

by using var here, the runtime Object class is being overwritten. I'm curious if this is done intentionally. If it is intentional, is the code extending the default Object or replacing it fully?

This Object declaration is both intentional and unfortunate. The reason Object is defined this way is due Babel transforms not qualifying globalThis.Object in the module header polyfill. There were issues related to "Object used before initialization" when TypeBox declared the Object with const. The following is the high level summary.

// Babel Polyfill Header
Object.defineProperty(....)   // <--- 'Object used before initialization error here

// TypeBox export
export const Object = _Object // <--- Because Object is defined as 'const' here

There were two solutions available.

• Babel updates their polyfill to correctly qualify the Object with globalThis or global
• TypeBox uses a var declaration

I went with the latter option as it wasn't really feasible for Babel to use globalThis to qualify Object (as globalThis is relatively new, and Babel likely needs downlevel transformations to older ES targets, making the resolution of the Object global overly excessive)

---

As for the _Object declaration of the function. I recall that being done for React Native, but can't remember the details around it.

---

The declaration of Object is largely an annoying bit of trivia TypeBox carries around and unfortunately, there are too many downstream tools that hang various logic off the non-qualified Object. TypeBox doesn't really have option other than to fudge the declaration, but certainly would be open to alternative way to declare, particularly for such a critical type.

Hope this brings some insight
Cheers
S

[tylersayshi]

got it, thanks!