default is undefined

http://stackoverflow.com/questions/41785777/webpack-and-ts-loader-bundle-returning-typeerror-on-third-party-library/41786585#41786585

I've written about this a few times. About time I add somewhere in this book :rose:

Start with the linked Stack Overflow question and answer to understand the reported “default is undefined” behavior, then find the relevant place in the TypeScript book. Done means adding a clear explanation of this issue to the book and confirming that it fits the surrounding content.

Written by the indexing model from the issue text.