Enable ESLint

[adroitwhiz]

This PR enables ESLint and lints the codebase with it.

The linting rules used are the "recommended" settings for ESLint, with the following exceptions:

• Semicolons are required. By default, ESLint doesn't take a position on the explicit semicolons/automatic semicolon insertion debate, and since this codebase uses semicolons, ESLint should enforce that usage consistently.
• Unused variables are allowed, owing to the number at which they are currently present in the codebase.

The vast majority of fixes fall into the following categories:

• Removing unnecessary regex escapes
• Removing unnecessary double negations
• Making var scoping more explicit
• Not redeclaring function arguments as vars
• Adding missing semicolons
• Removing irregular whitespace

There are a few changes that may affect code behavior:

• In path.js, a global variable leak has been fixed (the variable v was missing a var statement and hence leaking into global scope)
• In webgl.js, one use of the undefined max function (I confirmed with a debugger that it's not defined in that scope) was replaced with Math.max
• In two.js line 1335, a loop that changed the value of i given by 'forEach' now uses the j variable--not sure if that changes anything
• In getAnchorsFromArcData (two.js line 2125), the unused 'matrix' variable declaration has been removed
• In Two.Utils.Events.trigger (two.js line 2321), ev has been changed to event. ev was not defined.

[jonobr1]

This is awesome, thanks! I'll check two.js line 1335 to make sure that changing i to j is not a problem.

[jonobr1]

Just to confirm it lines everything that's not in the overrides?

[adroitwhiz]

The overrides mean "apply these linting rules to only these specific files".

I'm using it here so it knows that "utils" and "tests" are running in Node, and "tests" has some QUnit-related global variables (ESLint will otherwise complain about accessing undeclared global variables).

[adroitwhiz]

Since QUnit runs in the browser, I've removed it from the "env": {"node": true} override.

[jonobr1]

I'll add linting as a step in the build script 🙇

[jonobr1]

This has been merged, but actually I'm getting errors when trying to lint. "ESLint couldn't find the config "airbnb-base" to extend from. Please check that the name of the config is correct."

Is that something you have npm installed globally?

[adroitwhiz]

I'm not sure--there's nothing Airbnb-related in the .eslintrc.json, and no Airbnb-related dependencies that appear in ESLint's dependencies.

Are you running the version of eslint this project depends on with npm run lint or ./node_modules/.bin/eslint, or are you running a globally-installed eslint? The latter may do weird things.

[jonobr1]

I deleted my node_modules folder, ran npm install, and then npm run lint. I can pull a full error log.

[adroitwhiz]

An error log would be helpful; I can't seem to reproduce this on Linux or Windows.

[jonobr1]

It was an issue with me. I keep a /junk folder in the project to add and test other aspects of Two.js and was using webpack and rollup. In there I was referencing airbnb-base. A simple ignore of /junk in the eslintrc.json fixed that.