function watch() {
  return gulp.watch('src/*.js', gulp.series(clean, build));
}
/*.js', 'test/*.js' ])
    .pipe(eslint())
    .pipe(eslint.formatEach())
    .pipe(eslint.failOnError());
}


function clean() {
  return del('lib/**');
}


function build() {
  return gulp.src('src/*