How to use the uglify-js.OutputStream function in uglify-js

var compressor = UglifyJS.Compressor({});
var compressed_ast = toplevel.transform(compressor);

compressed_ast.figure_out_scope();
compressed_ast.compute_char_frequency();
compressed_ast.mangle_names();

var stream = UglifyJS.OutputStream({});
compressed_ast.print(stream);
var code = stream.toString(); // this is your minified code

var code = compressed_ast.print_to_string({});

var source_map = UglifyJS.SourceMap({});
var stream = UglifyJS.OutputStream({
    //...
    source_map: source_map
});
compressed_ast.print(stream);

var code = stream.toString();
var map = source_map.toString(); // json output for your source map

var compressor = UglifyJS.Compressor({});
var compressed_ast = toplevel.transform(compressor);

compressed_ast.figure_out_scope();
compressed_ast.compute_char_frequency();
compressed_ast.mangle_names();

var stream = UglifyJS.OutputStream({});
compressed_ast.print(stream);
var code = stream.toString(); // this is your minified code

var code = compressed_ast.print_to_string({});

var source_map = UglifyJS.SourceMap({});
var stream = UglifyJS.OutputStream({
    //...
    source_map: source_map
});
compressed_ast.print(stream);

var code = stream.toString();
var map = source_map.toString(); // json output for your source map

exports.minify = function(files, dest, options) {
    options = options || {};

    grunt.verbose.write('Minifying with UglifyJS...');

    var topLevel = null;
    var totalCode = '';

    var outputOptions = getOutputOptions(options, dest);
    var output = UglifyJS.OutputStream(outputOptions);

    // Grab and parse all source files
    files.forEach(function(file){
      var code = grunt.file.read(file);
      if (typeof options.sourceMapPrefix !== 'undefined') {
        file = file.replace(/^\/+/, "").split(/\/+/).slice(options.sourceMapPrefix).join("/");
      }
      totalCode += code;
      topLevel = UglifyJS.parse(code, {
        filename: file,
        toplevel: topLevel
      });
    });

    // Wrap code in a common js wrapper.
    if (options.wrap) {

// Mangling

		compressed_ast.figure_out_scope();
		compressed_ast.compute_char_frequency();
		compressed_ast.mangle_names();

		// output file

		var source_map_options = {
			file: path.basename(minifiedOutputPath),
			root: 'src'
		};

		var source_map = uglify.SourceMap( source_map_options )
		var stream = uglify.OutputStream( {
			source_map: source_map,
			comments: new RegExp( LICENSE )
		} );

		compressed_ast.print( stream );
		var code = stream.toString();

		console.log( '  Writing minified output: ' + minifiedOutputPath );

		fs.writeFileSync( minifiedOutputPath, code + sourcemapping, 'utf8' );

		if ( args.sourcemaps ) {

			console.log( '  Writing source map.' );

			fs.writeFileSync( sourcemapPath, source_map.toString(), 'utf8' );

ast.figure_out_scope()

  const compressed = ast.transform(compressor)

  if (mangle) {
    compressed.figure_out_scope()
    compressed.compute_char_frequency()
    compressed.mangle_names()
  }

  const outSourceMap = new UglifyJS.SourceMap({
    file: `${id}.js`,
    root: sourceRoot
  })

  const stream = new UglifyJS.OutputStream({
    ascii_only: true,
    screw_ie8: false,
    source_map: outSourceMap
  })
  /* eslint-enable camelcase */
  compressed.print(stream)

  const js = stream.toString()
  const map = JSON.parse(outSourceMap.toString())
  const generator = new SourceMapGenerator.fromSourceMap(new SourceMapConsumer(map))
  sourceMaps.forEach(function(sourceMap) {
    generator.applySourceMap(new SourceMapConsumer(sourceMap), sourceMap.sources[0], sourceRoot)
  })

  return {
    js,

if (!process.env.DEBUG) {
      // Parse.
      var ast = uglify.parse(compiledSource);

      // Compress.
      ast.figure_out_scope();
      ast.transform(uglify.Compressor());

      // Mangle.
      ast.compute_char_frequency();
      ast.figure_out_scope();
      ast.mangle_names();

      // Output.
      var stream = uglify.OutputStream({ source_map: null });
      ast.print(stream);

      var source = '(function(window,document){' +
        stream + '})(window,document);';
      obj.buffer = new Buffer(source, 'utf8');

    } else {
      obj.buffer = new Buffer(compiledSource, 'utf8');
    }
  }

}
            res.push(ist.inject('line', subNode.start.line));
          } else if (subNode instanceof Uglify.AST_Var) {
            res.push(ist.inject('line', subNode.start.line));
          }
          res.push(subNode);
        }
        node.body = res;
      }
    });
    // figure_out_scope
    ast.figure_out_scope();
    // walk process
    ast.walk(walker);

    var out = Uglify.OutputStream({
      preserve_line : true,
      comments: 'all',
      beautify: true
    });
    // rebuild file
    ast.print(out);
    this.code = out.toString();
    return this;
  },
  /**

format: 'umd',
    sourceMap: true,
    sourceMapFile: pkg.name + '.js',
    moduleName: 'L.esri.Heat',
    globals: {
      'esri-leaflet': 'L.esri'
    }
  });

  var sourceMap = UglifyJS.SourceMap({
    file: pkg.name + '.js',
    root: process.cwd(),
    orig: JSON.parse(transpiled.map)
  });

  var stream = UglifyJS.OutputStream({
    preamble: copyright,
    source_map: sourceMap
  });

  UglifyJS.parse(transpiled.code).print(stream);

  var code = stream.toString();
  var map = sourceMap.toString().replace(new RegExp(path.join(process.cwd(), 'src'), 'g'), '../src');

  fs.writeFileSync(path.join('dist', pkg.name + '.js'), code + '\n//# sourceMappingURL=./' + pkg.name + '.js.map');
  fs.writeFileSync(path.join('dist', pkg.name + '.js.map'), map);
  process.exit(0);
}).catch(function (error) {
  console.log(error);

}).then(function (bundle) {
  var transpiled = bundle.generate({
    format: 'umd',
    sourceMap: true,
    sourceMapFile: pkg.name + '.js',
    moduleName: 'L.esri'
  });

  var sourceMap = UglifyJS.SourceMap({
    file: pkg.name + '.js',
    root: process.cwd(),
    orig: JSON.parse(transpiled.map)
  });

  var stream = UglifyJS.OutputStream({
    preamble: copyright,
    source_map: sourceMap
  });

  UglifyJS.parse(transpiled.code).print(stream);

  var code = stream.toString();
  var map = sourceMap.toString().replace(new RegExp(path.join(process.cwd(), 'src'), 'g'), '../src');

  fs.writeFileSync(path.join('dist', pkg.name + '.js'), code + '\n//# sourceMappingURL=./' + pkg.name + '.js.map');
  fs.writeFileSync(path.join('dist', pkg.name + '.js.map'), map);
  process.exit(0);
}).catch(function (error) {
  console.log(error);