GruntJs is a task-based command line build tool for JavaScript projects. Grunt is a JavaScript task runner that automates your routine development tasks. While working on your web application you do a lot of tasks like code linting, minification, merging manually. But Grunt will let you create automatic tasks for all of these (and more) manual processes.
Bower is a package manger for frontend application development. Bower manages all your dependencies like JavaScript and CSS libraries and plugins. This tutorial will help you getting started with Bower and use it in your project.
JSCS allows you to check the style errors in your javascript code. JSCS enforces rules from Google, jQuery, AirBnb, Crockford and many others. JSCS enables the common conventions and styling througout a team or project so that JavaScript code remains consistent.