grunt-express-server with grunt-contrib-watch

Gruntfile.js

module.exports = function(grunt) {

    var PROJ_ROOT  = __dirname;
    var BUILD_ROOT = PROJ_ROOT + '/build';

    var pkg = grunt.file.readJSON('package.json');
    var pkgDependencies = Object.keys(pkg.dependencies).map(function(val) {
        return 'node_modules/' + val + '/**';
    });

    grunt.initConfig({

        // Define the app's package.json file.
        pkg: pkg,

        // Delete the /build directory.
        clean: [BUILD_ROOT],

        // Copy everything into /build. The tasks are broken out
        // so we can re-run later through our watch tasks.
        copy: {
            appDependencies: {
                expand: true,
                cwd: PROJ_ROOT,
                src: pkgDependencies,
                dest: BUILD_ROOT
            },
            app: {
                expand: true,
                cwd: PROJ_ROOT,
                src: ['index.js', 'src/**', 'config/**'],
                dest: BUILD_ROOT
            }
        },

        // Watch for changes to src files and run the relevant
        // build commands. Only livereload when /build changes.
        watch: {
            app: {
                files: [
                    PROJ_ROOT + '/index.js',
                    PROJ_ROOT + '/src/**/*.js',
                    PROJ_ROOT + '/config/**/*'
                ],
                tasks: ['copy:app', 'express:dev'],
                options: {
                    spawn: false
                }
            },
        },

        // Run the server from /build.
        express: {
            dev: {
                options: {
                    script: BUILD_ROOT + '/index.js',
                    port: 8080,
                    debug: true
                }
            }
        }
    });

    grunt.loadNpmTasks('grunt-contrib-clean');
    grunt.loadNpmTasks('grunt-contrib-copy');
    grunt.loadNpmTasks('grunt-contrib-watch');
    grunt.loadNpmTasks('grunt-express-server');

    grunt.registerTask('default', [
        'clean',
        'build',
        'run'
    ]);

    grunt.registerTask('build', [
        'copy'
    ]);

    grunt.registerTask('run', [
        'express:dev', 'watch'
    ]);
};