Minify JavaScript with UglifyJS3.

Install package with NPM and add it to your development dependencies:

npm install --save-dev gulp-uglify

var gulp = require('gulp');
var uglify = require('gulp-uglify');
var pipeline = require('readable-stream').pipeline;

gulp.task('compress', function () {
  return pipeline(
        gulp.src('lib/*.js'),
        uglify(),
        gulp.dest('dist')
  );
});

To help properly handle error conditions with Node streams, this project recommends the use of pipeline, from readable-stream.

Most of the minify options from the UglifyJS API are supported. There are a few exceptions:

1. The sourceMap option must not be set, as it will be automatically configured based on your Gulp configuration. See the documentation for Gulp sourcemaps.

gulp-uglify emits an 'error' event if it is unable to minify a specific file. The GulpUglifyError constructor is exported by this plugin for instanceof checks. It contains the following properties:

• fileName: The full file path for the file being minified.
• cause: The original UglifyJS error, if available.

Most UglifyJS error messages have the following properties:

• message (or msg)
• filename
• line

To see useful error messages, see Why Use Pipeline?.

By default, gulp-uglify uses the version of UglifyJS installed as a dependency. It's possible to configure the use of a different version using the "composer" entry point.

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

var minify = composer(uglifyjs, console);

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

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