Linting

[brettz9]

A large PR as it fixes the linting issues per your current desired config.

Re disabling:

1. I added a few disable directives such as for the complexity and max-statements rules, though I can undo that if you like.
2. I also inline-disabled a few cases of no-continue, as for longer code, continue helps prevent overly nested blocks. (Let me know if you prefer to have this rule removed.)
3. I also disabled no-ternary as I hope you'd reconsider not enforcing this (just restricting nested ternaries), though I can re-enable that and offer fixes if you are set on that.
4. I wasn't sure if I could change clk_x and clk_y to camel-casing without introducing a breaking change, so I explicitly ignored them in the camel-case rule, but let me know if I can change.

• Linting: Apply existing rules
• Linting: Add .eslintignore file (allows linting IDEs to know what should not be linted)
• Linting: Use overrides for special treatment of config files
• Linting: Remove no-undefined rule (not useful in strict mode and with no-restricted-names protecting against shadowing; while useful to use undefined for explicit array return)
• Linting: Comment out no-invalid-this (not practical for jQuery)
• Linting: Comment out no-ternary (really want to disable?)
• Linting: Allow clk_x and clk_y non-camel-cased
• Linting (HTML): Add self-closing tag for non-void <option>; add DOCTYPE; consistent/fixed quotes
• Docs: Remove stray quote in CONTRIBUTING (tripping up syntax highlighting in Atom)
• Refactoring/Linting: Throw Error object in place of "abort" string
• Refactoring: Prefer Array.isArray, move let/const closer to scope
• npm: Add lint and test script
• npm: Add eslint devDep.
• npm: - Bump engines to Node 8 (for Object.values); bump jquery dep. to earliest npm version 1.9.1 (though package.json started in 1.8.0)

If you need a build step so as to convert const to var and for..of for older browsers, I can look to add Babel to the build steps, though in so doing, and if it's all right, I'd like to:

1. Switch from grunt to package.json scripts only
2. Switch from PhantomJS to Cypress (which supports Chrome/Edge/Electron and Firefox) can also give code coverage).
3. If you want a build step, I'd think we could switch source to ESM in the process, and I can offer a build for that by Rollup if you are open to it.
4. (I also added Object.values, so for older browsers, that may need a polyfill, depending on what you wanted to do about such, e.g., to refer users to core-js if they need these.)

Other items I might tackle if you're ok with it:

1. If you want much tighter ESLint checks (while accommodating your current stylistic preferences), I might propose my own eslint-config-ash-nazg for a very robust config (drawing together several plugins in the community).
2. I'd also like to use husky, possibly with lint-staged to avoid the need for handling installation of shell scripts in the repo (keeping it all nicely Node or package.json command driven).

I'm on a very slow connection atm, so not able to download PhantomJS to confirm tests are still passing, but I think if you find any issues, there really shouldn't be many (or I can explain).

[brettz9]

Any chance you'll be able to take a look?

[brettz9]

Hi--I'd like to possibly make some more substantial contributions, but figure it is safer to build on a well-linted foundation.

[mgaert]

Is it possible to integrate this pull request? because it is hard to work on JQuery3 stuff if it is not lint error free!!