Holder
Holder renders image placeholders entirely on the client side.
Gulp
The streaming build system
Csscomb.js
CSS coding style formatter
Rulers Guides.js
Creates Photoshop-like guides and rulers interface on a web page
Nightwatch
UI automated testing framework based on node.js and selenium webdriver
Js Cover
JSCover is a tool that measures code coverage for JavaScript programs.
Bluebird
Bluebird is a full featured promise library with unmatched performance.
Blaver
A JavaScript library built on top of the Faker.JS library. It generates massive amounts of fake data in the browser and node.js.
Jasmine
DOM-less simple JavaScript testing framework
Trace Kit
Attempts to create stack traces for unhandled JavaScript exceptions in all major browsers.
Angular Debaser
Just a better way to test AngularJS apps.
Spa Eye
Backbone debugger for Firefox
Qunit
An easy-to-use JavaScript Unit Testing framework.
Stacktrace.js
Framework-agnostic, micro-library for getting stack traces in all web browsers
Grunt
Grunt: The JavaScript Task Runner
Fast Check
Property based testing framework for JavaScript (like QuickCheck) written in TypeScript
Browser Sync
Keep multiple browsers & devices in sync when building websites. http://browsersync.io