anchor.diff:  java -cp "cljs.jar;src" -m cljs.main -c hello-world.core -r
   ----
   
  +`-m`, which is short for `--main` invokes a Clojure function, in this case
  +`cljs.main`. The `cljs.main` function supports a variety of command line
  +arguments to specify common tasks. We're using `-c` for `--compile` to specify
  +that we want to compile the `hello-world.core` name space. This is followed by
  +`-r` for `--repl` to say that want a REPL to start immediately when compilation
  +completes.
  +
   Your default web browser will open to a page that looks like the following:
   
   After a couple of seconds you will see `Hello world!` print at the terminal and
  
positive.code: npm install source-map-support
  ----
  
  Let's build your Node project:
  
  [source,bash]
  ----
  
negative.code: (println "Hello world!")
  ----
  
  Let's create a release build. We can do this with `-O` for `--optimizations`.
  The default optimization level is `none`, but this time we want to use all
  optimizations provided by both ClojureScript and Google Closure Compiler - this
  can be done by specifying `advanced`. Other valid options for `-O` are
  `whitespace` and `simple` but these are less commonly used:
  
  [source,clojure]
  ----
  