Enable customizing the nrepl websocket port

* Fixes #140

doc/nrepl/README.md

@@ -42,6 +42,16 @@ you should be able evaluate expressions in `playground.cljs`. See a demo
 Note that the nREPL server connection stays alive even after the browser window
 refreshes.
 
+### Custom host address
+
+By default, the browser will connect to a websocket on the same host as it is loaded
+from, using `window.location.hostname`. If you need something else you can specify
+that setting the window variable `SCITTLE_NREPL_WEBSOCKET_HOST` like so:
+
+``` html
+<script>var SCITTLE_NREPL_WEBSOCKET_HOST = 'localhost';</script>
+```
+
 ### CIDER
 
 Choose `cider-connect-cljs`, select port `1339`, followed by the `nbb` REPL

src/scittle/nrepl.cljs

@@ -8,7 +8,9 @@
 
 (when-let [ws-port (.-SCITTLE_NREPL_WEBSOCKET_PORT js/window)]
   (set! (.-ws_nrepl js/window)
-        (new js/WebSocket (ws-url (.-hostname (.-location js/window)) ws-port "_nrepl"))))
+        (new js/WebSocket (ws-url (or (.-SCITTLE_NREPL_WEBSOCKET_HOST js/window)
+                                      (.-hostname (.-location js/window)))
+                                  ws-port "_nrepl"))))
 
 (when-let [ws (nrepl-server/nrepl-websocket)]
   (set! (.-onmessage ws)