housekeeping in main.js

adding some comments

restructured keylisteners

static/main.js

@@ -1,4 +1,7 @@
+
 var localModeEnabled = false;
+
+// References to howler objects 
 var howlerSounds = [];
 
 function ready(fn) {
@@ -58,6 +61,13 @@ ready(function() {
 	reset.addEventListener("click", resetSearch, false);
 	sounds_nav.addEventListener("click", resetSearch, false);
 
+	addKeyListeners();
+});
+
+/*
+* Adds all necessary KeyListeners to document
+*/
+function addKeyListeners() {
         // keyboard listener for global key strokes/inputs
         document.onkeydown = function(evt) {
                 evt = evt || window.event;
@@ -68,12 +78,14 @@ ready(function() {
                         // ctrl+k and ctrl+c key binding
                         killAllAudio();
                 } else if (evt.keyCode == 88 && evt.ctrlKey){
+                        // ctrl+x key binding
                         toggleLocalMode();
                 }
         };
 
+
         // TODO: make sure that only sound buttons get selected, not ALL a-tags. See d4377e0f49dc8dd5787f4466c9ab7f7e7cd37ec5#note_857
-	// keyboard listener for enter key
+        // keyboard listener for playing sounds using enter key
         var all_a_s = document.getElementsByTagName("a");
         for(i=0; i<all_a_s.length; i++) {
             all_a_s[i].addEventListener('keypress', async function (e) {
@@ -92,8 +104,7 @@ ready(function() {
                     }
                 });
         }
-
+}
-});
 
 
 function resetSearch() {
@@ -108,6 +119,9 @@ function resetSearch() {
 	searchfield.focus();
 }
 
+/*
+* Reads the stream url from input with id #streaming-url and forwards it to the server using AJAX.
+*/
 function playStream(){
 	var streamUrl = document.querySelector("#streaming-url").value;
 	ajaxRequest("/?video="+encodeURI(streamUrl));	
@@ -128,11 +142,15 @@ function ajaxRequest(url){
         ajaxRequest.open("GET", url, true);
         ajaxRequest.send(null);
     }catch (e){
-        alert("Your browser broke!");
+        alert("Unfortunately we were unable to handle your request. Please try again later and contact the server administrator if the problem persists.");
         return false;
     }
 }
 
+/*
+* Switches between local and remote playback mode.
+* Additionally changes the button text and its color so that the user has a visible feedback.
+/*
 function toggleLocalMode(){
 	toggleButton = document.getElementById("local-mode-button").children[0];
 	if(localModeEnabled){
@@ -148,6 +166,9 @@ function toggleLocalMode(){
 	}	
 }
 
+/*
+* Either plays the given sound file locally by using howler.js or forwards the request to the remote server using AJAX.
+*/
 function playSound(filename){
 	if(localModeEnabled){
 		// play local audio using howler.js
@@ -167,6 +188,9 @@ function killAllHowlerAudio(){
 	}	
 }
 
+/*
+* Kills all local or remote audio, depending on localModeEnabled
+*/
 function killAllAudio(){
 	if (localModeEnabled) {
         	killAllHowlerAudio();