gulpfile.js

'use strict';

const gulp        = require('gulp'),
    isDevelopment = false,  // (! process.env.NODE_ENV) || ('development' === process.env.NODE_ENV),
    DIR_DEST      = 'dist',
    DIR_TESTS     = 'tests',
    SRC_CSS       = 'app/scss/**/*.scss',
    SRC_JS        = 'app/js/**/*.js',
    TASK_BUILD    = 'build',
    TASK_CSS      = 'css',
    TASK_JS       = 'js',
    TASK_LIVE     = 'live',
    TASK_SERVE    = 'serve',
    TASK_WATCH    = 'watch';

function lazyRequireTask(taskName, options) {
    const path = './tasks/' + taskName.replace(/:/g, '-');
    options = options || {};
    options.taskName = taskName;
    options.isDevelopment = isDevelopment;
    gulp.task(taskName, function(callback) {
        let task = require(path).call(this, options);
        return task(callback);
    });
}

lazyRequireTask(TASK_CSS, {
    src:   SRC_CSS,
    dest:  DIR_DEST,
});

lazyRequireTask(TASK_CSS + ':min', {
    src:   SRC_CSS,
    dest:  DIR_DEST,
});

lazyRequireTask(TASK_JS, {
    src:   SRC_JS,
    dest:  DIR_DEST,
});

lazyRequireTask(TASK_JS + ':build', {
    src:   SRC_JS,
    dest:  DIR_DEST,
});

lazyRequireTask(TASK_JS + ':hint', {
    src:   SRC_JS,
});

lazyRequireTask(TASK_JS + ':lint', {
    src:   SRC_JS,
    dest:  DIR_DEST,
    cacheFilePath: process.cwd() + '/tmp/lintCache.json',
});

lazyRequireTask(TASK_JS + ':min', {
    src:   SRC_JS,
    dest:  DIR_DEST,
});

// gulp.task(TASK_BUILD, gulp.parallel(TASK_CSS, TASK_CSS + ':min', gulp.series(TASK_JS + ':lint', TASK_JS, TASK_JS + ':min')));
// gulp.task(TASK_BUILD, gulp.parallel(TASK_CSS, TASK_CSS + ':min', TASK_JS + ':build'));
gulp.task(TASK_BUILD, gulp.series(TASK_JS, TASK_JS + ':min'));

lazyRequireTask(TASK_SERVE, {
    server: {
    //    baseDir: '.',
        index: DIR_TESTS + '/index.html',
    },
});

gulp.task(TASK_WATCH, function() {
    gulp.watch(SRC_CSS,  gulp.parallel(TASK_CSS, TASK_CSS + ':min'));
//    gulp.watch(SRC_JS,   gulp.series(TASK_JS + ':lint', TASK_JS, TASK_JS + ':min'));
    gulp.watch(SRC_JS,   gulp.parallel(TASK_JS + ':build'));
});

gulp.task(TASK_LIVE, gulp.parallel(TASK_WATCH, TASK_SERVE));

gulp.task('dev', gulp.series(TASK_BUILD, TASK_LIVE));

gulp.task('default', function() {
});