Grunt__combine_concat.js

npm install grunt-contrib-uglify --save-dev
// root
  // tasks
    // options
      // uglify.js
module.exports = {
  dist: {
    src: [
      // files to combine
      'js/*',
    ],
    // destination
    dest: 'build/production.js'
  }
};


// finally add the task to your Gruntfile.js
grunt.registerTask('default', ['uglify']);