Joi.string().pattern() fails when dealing with different contexts

[CS-Birb]

Support plan

• is this issue currently blocking your project? (yes/no): Not at present
• is this issue affecting a production system? (yes/no): No

Context

• node version: v14.15.5
• module version with issue: v17.4.2
• last module version without issue: N/A
• environment (e.g. node, browser, native): Node & Browser
• used with (e.g. hapi application, another framework, standalone, ...): Universal (SSR) Nuxt Application
• any other relevant information:

What are you trying to achieve or the steps to reproduce?

Due to different global contexts, .pattern() fails in certain scenarios, I.e. Server-side rendering using Nuxt. However, this could be achieved just as simply using a subwindow with window.open()

I.e.

const a = window.open();
console.log(a.RegExp == RegExp); // false

const b = /123/;
console.log(b instanceof a.RegExp); // false

https://github.com/sideway/joi/blob/63b324497f03d9d39612b404da157e81d9c5aea9/lib/types/string.js#L531 Joi's current assertion is that regex instanceof RegExp, but as seen above this fails in niche (but valid, and not altogether uncommon) usecases. While not as safe, other alternatives could be to assert regex?.constructor.name === "RegExp" or to produce a new regex in the validating context RegExp(regex). Which approach is most desirable is your call, naturally.

What was the result you got?

regex must be a RegExp error.

What result did you expect?

To have a functional validation schema using .regex() across contexts.

[CS-Birb]

Further notes about this quirk with instanceof available at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/instanceof#instanceof_and_multiple_context_e.g._frames_or_windows

[stonega]

The issue still exist