Start using Grunt in your WordPress plugins and themes with npm. You can use in your theme and plugins by changing the paths in Grunt.js file.
Tools Used
Grunt : Javascript tsk runner for automation. Grunt and Grunt plugins are installed and managed via npm, the Node.js package manager. Grunt 0.4.x requires stable Node.js versions >= 0.8.0. Odd version numbers of Node.js are considered unstable development versions. http://gruntjs.com/getting-started
Step #1: Go to your project directory and install the dependencies from node_modules directory, [sudo] npm install
Step #2: Now run command "Grunt". It will run tasks added in Grunt.js file. Grunt will watch the changes you are making in js and scss files.