app/assets/javascripts contains vendor libraries and scripts that:
a) are not used
b) are outdated, or
c) can be handled by package.json

Red flags:

• app/assets/javascripts/vendor/jquery-migrate-1.2.1.min.js
• app/assets/javascripts/vendor/colorbox/jquery.colorbox-min.js vs. app/assets/javascripts/vendor/colorbox/jquery.colorbox.js
• app/assets/javascripts/components/style_settings_control.js (unused selectors, maybe whole file unused)
• app/assets/javascripts/plan.js (not imported anywhere, it looks like it was used for legacy bulk actions?)
• classes .show-trace-lr, .watch_infinity
• app/assets/javascripts/file_browser.js
• app/views/api/metric_visibilities/toggle_enabled.js.erb
• app/assets/javascripts/provider/signup_form.js
• app/assets/javascripts/extra_fields.js
• app/assets/javascripts/provider/admin/cms/intro.js.coffee (broken in master?)
• multi-part forms thing
• Mousetrap library (https://github.com/3scale/porta/pull/3775)