This is a version of Douglas Crockford's eponymous jsmin that also generates a <a href=https://github.com/ConradIrwin/ruby-source_map">source map so that you can debug your javascript as though it had never been minified at all!

Huge thanks should be given to Ryan Grove for porting Douglas Crockford's C code to Ruby so that I could ruin it :).

Installation

gem install source_map-jsmin

Creating a source map

    input = File.read("public/javascripts/myscript.js")

    map = SourceMap::JSMin.minify(input, :input_filename => "myscript.js",
                                         :output_filename => "myscript.min.js",
                                         :source_root => "http://localhost:3000/javascripts/"
                                 )

    # Output the minified code to a file for serving
    File.open("public/javascripts/myscript.min.js", "w"){ |f| f << map.generated_output }

    # Output the map to a file in the same manner
    File.open("public/javascripts/myscript.map.json", "w"){ |f| f << map.to_s }

Using a source map

In summary, you need to serve public/javascripts/myscript.min.js with an extra HTTP header: X-SourceMap: /javascripts/myscript.map.json, and enable source maps in the developer console of your Google Chrome 19+ web browser.

For more details try the source_map gem's README.

Future work

• I'd like to support passing an :input_sourcemap argument to minify so that if the input file was generated by a process that created a source map, the minification step will create a source map that refers to the original sources instead of to the intermediary input file.

License

This is all licensed under the MIT license, though it inherits Douglas Crockfords additional: "Must be used for good not evil" clause. If you have really pernickety lawyers this may cause you problems; but if you're actually using it for evil, you probably don't care too much.

Meta-fu

Contributions, bug reports and feature requests are welcome, though if they are to do with the core JSMIN please send them upstream and then notify me.