GruntJs is used for Task Runner.
What is Task runner why we use?
In one word: automation. The less work you have to do when performing repetitive tasks like minification, compilation, unit testing, linting, etc, the easier your job becomes. After you’ve configured it through a Gruntfile, a task runner can do most of that mundane work for you—and your team—with basically zero effort.
Who uses gruntjs:-
Refer here http://gruntjs.com/who-uses-grunt
Why use Grunt?
The Grunt ecosystem is huge and it’s growing every day. With literally hundreds of plugins to choose from, you can use Grunt to automate just about anything with a minimum of effort. If someone hasn’t already built what you need, authoring and publishing your own Grunt plugin to npm is a breeze.
The following series we explained step by step