tracing-framework : Rich tools for instrumenting, analyzing, and visualizing web apps.
PhantomJS : PhantomJS is a headless WebKit with JavaScript API. It has fast and native support for various web standards: DOM handling, CSS selector, JSON, Canvas...
nwb : A toolkit for React, Preact & Inferno apps, React libraries and other npm modules for the web, with no configuration (until you need it)
RegPack : RegPack is a packer intended for use on minified Javascript code.
It is mostly suited to small size constraints (1kb, up to 4kb).