Add ESLint and fix a few formatting errors

[pdehaan]

Currently ✖ 2 problems (0 errors, 2 warnings).

Once we land this and get the ESLint hook passing, we may want to add a npm script pretest hook that runs "pretest": "npm run lint" so ESLint will run automatically every time you run $ npm test or the build runs on Travis-CI. Done.

How to:

$ npm run lint

> blok@1.0.0 lint /Users/pdehaan/dev/github/mozilla/blok
> eslint .


/Users/pdehaan/dev/github/mozilla/blok/js/background.js
  185:11  warning  'actionPerformed' is defined but never used  no-unused-vars

/Users/pdehaan/dev/github/mozilla/blok/js/canonicalize.js
  28:7  warning  'isIP4Decimal' is defined but never used  no-unused-vars

✖ 2 problems (0 errors, 2 warnings)

r? @groovecoder

[pdehaan]

Not sure if we want to commit 3rd party code in the repo, versus use something like npm or bower.

[groovecoder]

Thanks for the tooling PR!

Based on feedback from other Mozilla webdevs, I had planned to try standard for coding style enforcement. Are these ESLint rules more aligned with other add-ons and Mozilla code-bases?

[groovecoder]

Hmm ... needs a rebase now ...

[groovecoder]

Superseded by #39 which includes the rebase.

[pdehaan]

Are these ESLint rules more aligned with other add-ons and Mozilla code-bases?

We have no conventions or shared Mozilla ESLint config [that I'm aware of]. It's all Wild West based on repo owner's preferences. I haven't used Standard in a while, but I'll see about a follow-on PR that tries adding eslint-config-standard.

[pdehaan]

Turns out injecting standard was pretty trivial by adding the eslint-config-standard config (and a couple plugins) as dev dependencies:

$ npm i eslint-config-standard eslint-plugin-{standard,promise} -D`

Then tweak the ESLint rules to extend the standard config:

extends:
  - eslint:recommended
  - standard

Finally run $ npm run lint -- --fix to run ESLint and auto-fix any auto-fixable errors:

$ npm run lint

> blok@1.0.0 lint /Users/pdehaan/dev/github/mozilla/blok
> eslint .

/Users/pdehaan/dev/github/mozilla/blok/js/background.js
    9:5   error    Identifier 'current_active_tab_id' is not in camel case          camelcase
   10:5   error    Identifier 'current_origin_disabled_index' is not in camel case  camelcase
   11:5   error    Identifier 'current_active_origin' is not in camel case          camelcase
   12:5   error    Identifier 'blocked_requests' is not in camel case               camelcase
   13:5   error    Identifier 'blocked_entities' is not in camel case               camelcase
   14:5   error    Identifier 'allowed_requests' is not in camel case               camelcase
   15:5   error    Identifier 'allowed_entities' is not in camel case               camelcase
   16:5   error    Identifier 'total_exec_time' is not in camel case                camelcase
   17:5   error    Identifier 'reasons_given' is not in camel case                  camelcase
   49:5   error    Identifier 'current_active_origin' is not in camel case          camelcase
   50:5   error    Identifier 'current_origin_disabled_index' is not in camel case  camelcase
   56:29  error    Identifier 'current_origin_disabled_index' is not in camel case  camelcase
  172:5   error    Identifier 'current_active_tab_id' is not in camel case          camelcase
  179:11  warning  'actionPerformed' is defined but never used                      no-unused-vars
  179:30  error    Identifier 'current_origin_disabled_index' is not in camel case  camelcase
  180:29  error    Identifier 'current_origin_disabled_index' is not in camel case  camelcase
  181:29  error    Identifier 'current_origin_disabled_index' is not in camel case  camelcase

/Users/pdehaan/dev/github/mozilla/blok/js/canonicalize.js
   1:70  error    Unnecessary escape character: \           no-useless-escape
   2:45  error    Unnecessary escape character: \           no-useless-escape
   3:71  error    Unnecessary escape character: \           no-useless-escape
  19:62  error    Unnecessary escape character: \           no-useless-escape
  26:7   warning  'isIP4Decimal' is defined but never used  no-unused-vars

/Users/pdehaan/dev/github/mozilla/blok/js/lists.js
  37:12  error  Identifier 'category_name' is not in camel case  camelcase
  39:9   error  Identifier 'entity_count' is not in camel case   camelcase
  41:25  error  Identifier 'entity_count' is not in camel case   camelcase
  44:16  error  Identifier 'entity_name' is not in camel case    camelcase
  47:18  error  Identifier 'main_domain' is not in camel case    camelcase
  50:15  error  Identifier 'domains_count' is not in camel case  camelcase
  52:31  error  Identifier 'domains_count' is not in camel case  camelcase
  53:37  error  Identifier 'main_domain' is not in camel case    camelcase

✖ 30 problems (28 errors, 2 warnings)

I may let somebody else pull the trigger on this, since it looks like somebody will better domain knowledge than me to refactor the variable names into camelcase (or disable the Standard camelcase rule, if appropriate).

---

(Without running with the --fix flag, you should get ✖ 70 problems (68 errors, 2 warnings) from ESLint after switching to standard.)

[pdehaan]

(Moved standard conversation to #40 instead of continuing in a closed PR.)