Bundlers

• webpack - Packs CommonJs/AMD modules for the browser.
• Parcel - Blazing fast, zero configuration web application bundler.
• Terser - parser, mangler and compressor toolkit for ES6+

Data Visualization

Runner

• two.js - A renderer agnostic two-dimensional drawing api for the web.

ES6

Other

• Babel (Formerly 6to5) - Turn ES6+ code into vanilla ES5 with no runtime.

I18n And L10n

Runner

• ttag - Modern javascript i18n localization library based on ES6 tagged templates and the good old GNU gettext.

Misc

Other

• You Don't Know JS - Possibly the best book written on modern JavaScript, completely readable online for free, or can be bought to support the author.

QA Tools

Runner

• JavaScript Standard Style - Opinionated, no-configuration style guide, style checker, and formatter

SDK

Other

• Spotify SDK - Entity oriented SDK to work with the Spotify Web API.