javascript
var gulp = require('gulp');
var uglify = require('gulp-uglify');
var pump = require('pump');

gulp.task('compress', function (cb) {
  pump([
        gulp.src('lib/*.js'),
        uglify(),
        gulp.dest('dist')
    ],
    cb
  );
});

		Preserve all comments in code blocks

		Attempts to preserve comments that likely contain licensing information,
		even if the comment does not have directives such as `@license` or `/*!`.

		Implemented via the [`uglify-save-license`](https://github.com/shinnn/uglify-save-license)
		module, this option preserves a comment if one of the following is true:

		1. The comment is in the *first* line of a file
		2. A regular expression matches the string of the comment.
				For example: `MIT`, `@license`, or `Copyright`.
		3. There is a comment at the *previous* line, and it matches 1, 2, or 3.

		Specify your own comment preservation function. You will be passed the
		current node and the current comment and are expected to return either
		`true` or `false`.

		Preserve comments that start with a bang (`!`) or include a Closure Compiler
		directive (`@preserve`, `@license`, `@cc_on`).
		Deprecated in favor of the `license` option, documented above.

javascript
var uglifyjs = require('uglify-js'); // can be a git checkout
                                     // or another module (such as `uglify-js-harmony` for ES6 support)
var minifer = require('gulp-uglify/minifier');
var pump = require('pump');

gulp.task('compress', function (cb) {
  // the same options as described above
  var options = {
    preserveComments: 'license'
  };

  pump([
      gulp.src('lib/*.js'),
      minifier(options, uglifyjs),
      gulp.dest('dist')
    ],
    cb
  );
});