anchor.diff:  specify `:output-dir` so that the REPL can reuse compiled files
   generated by the build.
   
  -We also need to modify our source to load the browser REPL:
  -
  -[source,clojure]
  -----
  -(ns hello-world.core
  -  (:require [clojure.browser.repl :as repl]))
  -
  -(defonce conn
  -  (repl/connect "http://localhost:9000/repl"))
  -
  -(enable-console-print!)
  -
  -(println "Hello world!")
  -----
  -
  -We create the connection with `defonce`. This ensures the connection is
  -constructed only one time - we may reload this namespace during
  -development and we don't want multiple connection instances.
  -
   Let's try it:
   
   [source,clojure]
  
positive.code: ----
  
  The first time will be somewhat slow as the REPL communication script
  needs to build. You will also see innocuous `WARNING`s from the Google
  Closure Compiler that can be ignored. You should eventually see the
  following message:
  
  [source,bash]
  ----
  
negative.code: [[node.js-repl]]
  === Node.js REPL
  
  Running a Node.js REPL is similar to running a browser REPL.
  Create a helper build file called `node_repl.clj` that looks like the
  following:
  
  