My Gruntfile.js sample

Gruntfile.js

module.exports = function(grunt) {
  grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),

    clean: ['static/assets/user/bare'],

    jshint: {
      files: ['Gruntfile.js', 'static/assets/user/js/**/*.js'],
      options: {
        globals: {
          jQuery: true
        }
      }
    },

    coffee: {
      options: {
        bare: true
      },
      compile: {
        files: {
          'static/assets/user/bare/js/coffee.js': ['static/assets/user/coffee/**/*.coffee']
        }
      }
    },

    concat: {
      options: {
        stripBanners: true,
        banner: '/*!\n' +
        ' * <%= pkg.name %>\n' +
        ' * <%= pkg.url %>\n' +
        ' * @author <%= pkg.author %>\n' +
        ' * @version <%= pkg.version %>\n' +
        ' * Copyright <%= pkg.copyright %>. <%= pkg.license %> licensed.\n' +
        ' */\n'
      },
      dist: {
        src: ['static/assets/user/bare/js/**/*.js', 'static/assets/user/js/**/*.js'],
        dest: 'static/assets/user/dist/js/script.js',
      }
    },

    uglify: {
      options: {
        mangle: {
          except: ['jQuery']
        }
      },
      dist: {
        options: {
          sourceMap: true,
          sourceMapName: 'static/assets/user/dist/js/script.map'
        },
        files: {
          'static/assets/user/dist/js/script.min.js': ['static/assets/user/dist/js/script.js']
        }
      }
    },

    less: {
      production: {
        options: {
          compress: true,
          cleancss: true,
          paths: ['static/assets/less']
        },
        files: {
          'static/assets/user/dist/css/style.css': 'static/assets/user/less/style.less'
        }
      }
    },

    watch: {
      options: {
        dateFormat: function(time) {
          grunt.log.writeln('The watch finished in ' + time + 'ms at' + (new Date()).toString());
          grunt.log.writeln('Waiting for more changes...');
        },
      },
      files: ['<%= jshint.files %>', 'static/assets/user/less/**/*.less', 'static/assets/user/coffee/**/*.coffee'],
      tasks: ['jshint', 'coffee', 'concat', 'uglify', 'less', 'clean']
    }
  });

  grunt.loadNpmTasks('grunt-contrib-jshint');
  grunt.loadNpmTasks('grunt-contrib-watch');
  grunt.loadNpmTasks('grunt-contrib-concat');
  grunt.loadNpmTasks('grunt-contrib-coffee');
  grunt.loadNpmTasks('grunt-contrib-uglify');
  grunt.loadNpmTasks('grunt-contrib-less');
  grunt.loadNpmTasks('grunt-contrib-clean');

  // for default task
  grunt.registerTask('default', ['jshint', 'coffee', 'concat', 'uglify', 'less', 'clean']);
};