Uncaught TypeError: (0 , o.default) is not a function: What's causing it?

Question

In my create react app project I'm running into the following error in my production build (not in my dev build):

Uncaught TypeError: (0 , o.default) is not a function at Object.e.f.(:4444/anonymous function)...

I've been investigating this bug for a couple of hours but struggle to find out how to debug this uglified piece of js.

What makes it tough is that the error returns o.default and not SomeLibrary.default so I don't really know where to start my search really...

What does that o.default mean in this case? Any tips for figuring out what's going wrong here?

Answer 1

It seems to be import statement somewhere in your file is incorrect.

Example: (from an issue)

// fails
import combineReducers from "redux"

// correct
import { combineReducers } from "redux"

What makes it tough is that the error returns o.default and not SomeLibrary.default so I don't really know where to start my search really...

There's nothing but exported in some library just as o. Example default export:

export default {
  o: something
}