What is the oxidation number of hydrogen in the compound NH3?

The assumed oxidation number of nitrogen in ammonia (3+) in this question, is wrongly signed:

The correct oxidation number if nitrogen in NITRIDES (like in ammonia NH3, ammonium NH4+ and amino groups -NH2) is minus 3, so hydrogen has oxidation value of plus 1(one, like in H+) which is in fact the only possible form when attached to nonmetals.