[removed] Quickly lookup value in object (like we can with properties)

Question

I have an object that has pairs of replacement values used for simple encoding / decoding (not for security, just for a convenience; too complicated to explain it all here).

Answer 1

You can create a reversed version of the mapping programmatically (instead of by hand) and use it instead.

var rev = {}
for (key in obj)
    rev[obj[key]] = key