Change isPlainObject to support objects created in a different context

[keeganstreet]

To resolve #3066

[kitten]

Like indicated in the PR, this will need to be Object.prototype.toString to support objects with toStrung, including Object.create(null) 🙌

[keeganstreet]

Ah yes of course, we can't call toString()if it doesn't exist on that object.

The problem I was trying to address by using x.toString() instead of Object.prototype.toString.call(x) was to call a custom toString when it exists:

class MyClass {
  toString() {
    return "[object MyClass]"
  }
}
const m = new MyClass();
Object.prototype.toString.call(m); // "[object Object]" <-- does not call the custom toString method
m.toString(); // "[object MyClass]"

I can solve this by using: (x.toString ? x.toString() : Object.prototype.toString.call(x)) === '[object Object]'

[keeganstreet]

Hi @kitten, are you happy with this now that it has been updated?

[shadforth]

Looking forward to seeing this in action! 👏

[quantizor]

LGTM