Gracefully handle Error instances without a stack property

[kmohrf]

This fixes #6. I’ve added a test and included some documentation why the stack property is checked.

I thought about simply casting error.stack to a string, but that didn’t seem like a good idea (who knows if there are more fun exceptions to the stack property like array values). So I ended up with validating it as a string or String object (both of which implement replace, so that should be fine).

Feel free to change anything to your liking!

Thanks!

[kmohrf]

typeof value === 'string' is enough. The stack can never be a Object-wrapped string.

With stack not being standardized it seems to me that it’s as likely a String object as it is undefined. I don’t see the point of omitting that specific case if support for it is already there.

Also, this way, it will lose information about error type. I would consider a better way to handle this.

I agree and have changed the implementation. If you still have something else in mind, please consider a more detailed expectation.

[kmohrf]

any further thoughts @sindresorhus?

[sindresorhus]

Thanks :)