ESLint https://github.com/eslint/eslint is a popular javascript linter. I created it on my own phabricator install for someone at work and it seems to have gained some traction in https://secure.phabricator.com/D12198 since the time I originally opened it. I also see that coursera seems to be using it on their fork of arcanist although that version features some changes that are not applicable to a wider audience.