setting example of compile html, css & javascript files.

Gruntfile.js

module.exports = function(grunt){

  var pkg = grunt.file.readJSON( 'package.json' );

  grunt.initConfig({

    pkg: pkg,

    clean: {
        build: [ '.tmp', 'dest' ],
        release: [ '.tmp' ]
    },

    copy: {
        html: {
            files: [ {
                expand: true,
                cwd: 'src',
                src: [
                  '*.html',
                  'assets/css/lib/*.*',
                  'assets/js/lib/*.*',
                  'assets/data/*.*',
                  'assets/img/*.*'
                ],
                dest: 'dest'
            } ]
        }
    },

    useminPrepare: {
       html: 'src/*.html',
       options: {
         dest:'dest'
       }
    },

    usemin: {
      html: 'dest/*.html',
      options: {
          dest: 'dest'
       }
    },

    htmlmin: {
        options: {
            removeComments: true,
            collapseWhitespace: true
        },
        files: {
            src: 'dest/index.html',
            dest: 'dest/dest.html'
        }
    },

    watch: {
        scripts: {
            files: [ 'src/assets/css/*.css', 'src/assets/js/*.js' ],
            tasks: [ 'build' ]
        }
    }

  });


  Object.keys( pkg.devDependencies ).forEach( function( devDependency ) {
      if( devDependency.match( /^grunt\-/ ) ) {
          grunt.loadNpmTasks( devDependency );
      }
  } );


  grunt.registerTask( 'build', [
    'clean:build',
    'copy',
    'useminPrepare',
    'concat',
    'uglify',
    'cssmin',
    'htmlmin',
    'usemin',
    'clean:release'
  ] );
  grunt.registerTask( 'default', [ 'watch' ] );

}

package.json

{
  "name": "repository_name",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "grunt": "^1.0.1",
    "grunt-contrib-clean": "^1.1.0",
    "grunt-contrib-concat": "^1.0.1",
    "grunt-contrib-copy": "^1.0.0",
    "grunt-contrib-cssmin": "^2.2.1",
    "grunt-contrib-htmlmin": "^2.4.0",
    "grunt-contrib-uglify": "^3.1.0",
    "grunt-usemin": "^3.1.1"
  }
}