Add code metric checks to .jshintrc

[Jörn Zaefferer]

JSHint supports a few code metric checks that we could adapt. Elijah has details here: ​http://www.elijahmanor.com/2012/09/control-complexity-of-your-javascript.html

Basically we'd add a variant of these:

"maxparams": 5,
"maxdepth": 5,
"maxstatements": 25,
"maxcomplexity": 10,

If we increase maxcomplexity to 13, its mostly datepicker and sortable left as offenders. We have to figure out which ones to address before adding these, and where to increase the numbers to accept what's there.

[Scott González]

The specific metrics need to be decided in conjunction with core.

[Scott González]

We'll stick with the numbers in the code block from the description. I made some progress on this today. For methods that use switch statements (like keydown event handlers) or independent if statements (like _setOption()) in a logical, we just increase the allowed cyclomatic complexity for those specific functions.

Still need to clean up the interactions and datepicker, plus one failure in the scale effect (too many statements).

[mikesherov]

I'm not a fan of maxstatements, and I'm not a fan of creating inline concessions for switch statements and independent ifs, as that opens a whole can of worms for inline linting comments. If the cyclomatic complexity is too high due to a switch statement, it's gotta be refactored.

That's just my thoughts.

[mikesherov]

Not doing this for now. May revisit someday in the future.