I tend to agree with the others. Warnings are your friends. As Sun Tzu said (and I paraphrase) "The best way to avoid a trap is knowing where it is". Generally, I'll not only 'use strict' and '-w' my stuff for everyday, but when developing, testing, and debugging, I'll 'use diagnostics' and fire up the 'ol debugger.

I especially like this if developing for a broad audience, web stuff included. The extra time and grief saves me tenfold down the line.

HTH
Dex

p.s. - YMMV ... TTOSBT (To thine own self be true).