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Comment by prodigal_erik | Hacker News Reader

Error.prototype.toString() reads e.name, not e.prototype.constructor.name, so you can't rely on everyone to have subclassed Error.

I'm not following, why can't I use:

   e instanceof Error

or:

   e instanceof MyError

why does toString() have anything to do with this?

It's very likely someone did

  const e = new Error('bad stuff happened')
  e.name = 'MyError'

without actually creating a MyError class to check with instanceof.

Unless it's common in popular libraries/packages, I don't see why I need to take it into account.

Which popular libraries do this?

If it's just in a few places, it should be handled specifically, and use sane choices in other places.

This is what I do when working with my own Error types.