isUndefined and isDefined should be used more consistently

[wnr]

I noticed the functions isUndefined and isDefined in src/Angular.js, which seems like a good idea to standardise the checking of defined/undefined variables. However, I noticed that still checks for undefined/defined are done without these functions in quite some places throughout the code. Have a look at the equals function defined in src/Angular.js around line 752, as an example. There the statement o2[key] !== undefinedcan be found. It seems to me that this should instead be isDefined(o2[key]) to keep the consistency and obey the defined/undefined check standardisation.

tl;dr; Only isDefinedand `isUndefined`` should be used the check for undefined/defined variables.

If this is desired, I would happily create a pull request fixing this.

[petebacondarwin]

I agree. I am looking into running jshint (or similar) against the code base as part of the build. This would help with this.