Minified Browserify bundle with sourcemap

gistfile1.js

var browserify = require('browserify');
var uglify = require('uglify-js');

var extract = require('convert-source-map');
var SourceMapGenerator = require('source-map').SourceMapGenerator;
var SourceMapConsumer = require('source-map').SourceMapConsumer;


browserify(
	'./src/index.js',
	{
		debug: true,
		basedir: base
	}
)
.bundle(function(err, compiled){
	if (!err){
		var browserified = compiled.toString('utf8');
		var sourcemap1 = extract.fromSource(browserified).toJSON();
		browserified = extract.removeComments(browserified);

		var minified = uglify.minify(browserified, {
			fromString: true,
			outSourceMap: 'index.js.map'
		});
		var sourcemap2 = minified.map;

		var combined = SourceMapGenerator.fromSourceMap(new SourceMapConsumer(JSON.stringify(sourcemap1)));
		combined.applySourceMap(new SourceMapConsumer(JSON.stringify(sourcemap2)));
		var sourcemap = JSON.stringify(combined.toJSON());

		// Resulting file contents
		console.log(minified.code); //index.js
		console.log(sourcemap); //index.js.map
	}
});