lucatros (9) [Avatar] Offline
On Listing 2.11 & 2.12 the underscore for the id is missing:

var query = { _id:'id') };

The character is there but for some reason is not visible on the PDF (at least this is the case on MAC on Acrobat DC).

It might be good to check other listings since I think the problem occurs throughout the PDF.

EDIT: I tried with Preview and it's looking OK. Seems to be a problem with Acrobat.
lucatros (9) [Avatar] Offline
Disregard. It's OK on MEAP v11.