Gist for "Java Build Tools, JavaScript Package Managers and Task Runners (Part 3)" blog-post.

Gruntfile.js

/* File: Gruntfile.js */

//wrapper function
module.exports = function(grunt) {

	//Project and task configuration.
	grunt.initConfig({
		//this task is responsible for deleting all files and sub-folders under the folder "/prod".
		clean: {
			//here we use a globbing pattern to match everything inside the `prod` folder
			prod: ['src/main/resources/prod/**/*']
		},
		//this task is responsible for minifying all JS files under "/dev"; with the result output in the "/prod" folder.
		uglify: {
			js: {
				files: [{
					//Option to create a one-to-one mapping of 'src' and 'dest' files.
					expand: true,
					//Source files: all files that match the wildcard are selected; excluding those with a trailing '.combo.js', '-min.js' and '.min.js'.
			    src: ['**/*.js', '!**/*.combo.js', '!**/*-min.js', '!**/*.min.js'],
					//Destination folder: where the processed files will be output.
				  dest: 'src/main/resources/prod',
					//Current working directory: from where the source files will be extracted.
				 	cwd: 'src/main/resources/dev',
					//the minified source is output with a trailing ".js"; after minification.
					ext: '.js'
				}]
			}
		}		
	});

	//Load plugins and tasks (installed using npm).
	grunt.loadNpmTasks('grunt-contrib-clean');
	grunt.loadNpmTasks('grunt-contrib-uglify');

	//create 'clean-log' task. This task is executed as per the task chain order below (see 'default' task). Its purpose is to output a log stating that the 'clean' task is executed next.
	grunt.registerTask('clean-log', function(){
		//log a message using grunt's "log" API.
		grunt.log.writeln('Cleaning \'prod\' folder from previously generated files.');		
	});

	//create 'uglify-log' task. This task is executed as per the task chain order below (see 'default' task). Its purpose is to output a log stating that the 'uglify' task is executed next.
	grunt.registerTask('uglify-log', function(){
		//log a message using grunt's "log" API.
 		grunt.log.writeln('Minifying custom JS files.')	
	});

	//register task/s with 'default'. Every specified task in 'taskList' will be executed, in the order specified; when 'grunt' is run from termeinal.
	grunt.registerTask('default', ['clean-log', 'clean', 'uglify-log', 'uglify:js']);
};