gulpfile.js

var fs = require('fs');

var del = require('del');
var browserSync = require('browser-sync');
var gulp = require('gulp');
var plugins = require('gulp-load-plugins')();
var runSequence = require('run-sequence');  // Temporary solution until Gulp 4
                                            // https://github.com/gulpjs/gulp/issues/355

var reload = browserSync.reload;

// ---------------------------------------------------------------------
// | Helper tasks                                                      |
// ---------------------------------------------------------------------

gulp.task('clean', function () {
    return del(['build']);
});

gulp.task('copy', [
    'copy:css',
    'copy:html',
    'copy:misc'
]);

gulp.task('copy:css', function () {
    return gulp.src('src/css/all.scss')
        .pipe(plugins.sass({ style: 'compressed' }))
        .pipe(gulp.dest('build/css'))
        .pipe(plugins.filter('**/*.css'))
        .pipe(reload({stream: true}));
});

gulp.task('copy:html', function () {
    return gulp.src([

        // Copy all `.html` files
        'src/*.html',

        // Exclude the following files since they
        // are only used to build the other files
        '!src/masthead.html',
        '!src/base.html'

    ]).pipe(plugins.swig({
        defaults: { cache: false },
        data: JSON.parse(fs.readFileSync("./src/data.json"))
    })).pipe(plugins.htmlmin({

        // In-depth information about the options:
        // https://github.com/kangax/html-minifier#options-quick-reference

        collapseBooleanAttributes: true,
        collapseWhitespace: true,
        minifyJS: true,
        removeAttributeQuotes: true,
        removeComments: true,
        removeEmptyAttributes: true,
        removeOptionalTags: true,
        removeRedundantAttributes: true,

        // Prevent html-minifier from breaking the SVGs
        // https://github.com/kangax/html-minifier/issues/285
        keepClosingSlash: true,
        caseSensitive: true

    })).pipe(gulp.dest('build')).pipe(reload({stream: true}));
});

gulp.task('copy:misc', function () {
    return gulp.src([

        // Copy all files
        'src/**',

        // Exclude the following files
        // (other tasks will handle the copying of these files)
        '!src/*.html',
        '!src/{css,css/**}',
        '!src/data.json'

    ], {
        // Include hidden files by default
        dot: true
    }).pipe(gulp.dest('build'));

});

gulp.task('browser-sync', function() {
    browserSync({

        // In-depth information about the options:
        // http://www.browsersync.io/docs/options/

        notify: false,
        port: 8000,
        server: "build",
        open: false
    });
});

gulp.task('watch', function () {
    gulp.watch(['src/**/*.scss'], ['copy:css']);
    gulp.watch(['src/*.html', 'src/data.json'], ['copy:html', reload]);
    gulp.watch(['src/img/**', 'src/demos/**'], ['copy:misc']);
});

// ---------------------------------------------------------------------
// | Main tasks                                                        |
// ---------------------------------------------------------------------

gulp.task('build', function (done) {
    runSequence('clean', 'copy', done);
});

gulp.task('default', ['build']);

gulp.task('serve', function (done) {
    runSequence('build', ['browser-sync', 'watch'], done);
});