gulp-useref to build js with npm managed libraries

Question

I'm using Yo Generator's web app as base to build something with PUG. However it's still reference to Bower. So I switch all needed JS package to npm. But this gulp task is ignoring all libraries in node_modules

gulp.task('html', ['views', 'styles', 'scripts'], () => {
  return gulp.src([
    'tmp/**/*.html',
    'app/**/*.html',
    '!app/layouts/**/*'
  ])
    .pipe($.useref({searchPath: [paths.tmp, paths.src, '.']}))
    .pipe($.if(/\.js$/, $.uglify({ compress: {drop_console: true} })))
    .pipe($.if(/\.css$/, $.cssnano({ safe: true, autoprefixer: true })))
    .pipe($.if(/\.html$/, $.htmlmin({
      collapseWhitespace: true,
      minifyCSS: true,
      minifyJS: {compress: {drop_console: true}},
      processConditionalComments: true,
      removeComments: true,
      removeEmptyAttributes: true,
      removeScriptTypeAttributes: true,
      removeStyleLinkTypeAttributes: true
    })))
    .pipe(gulp.dest('dist'));
});

is there a way to tell gulp-useref to combine js lib from this path /node_modules/

Answer 1

Turns out it's gulp-uglify doesn't like es6 such as "let" in some JS lib. So the solution is to use gulp-uglify-es instead.