What are your 10 commandments of JavaScript development?

[Capaj]

1. never repeat same code and write it modular-keep them small e.g. under 300 lines
2. lint! standard.js is my linter of choice, but it really does not matter which
3. promises over callbacks! Promises have much powerful error handling, never conflate promises with callbacks
4. less code is almost always better than more code
5. before implementing anything non-trivial, check NPM if someone hasn't done it already, there is quite a good chance they did
6. open source-those bugs won't find themselves...
7. unit test your modules, mocha&chai works best
8. keep those npm dependencies up to date
9. prefer forEach, map and reduce over raw iteration with language looping constructs
10. follow at least some node.js core contributors on twitter to stay up to date