Clean up JS

* remove unused variables/functions
* use the dot notation
* use explicit coercion
* remove unneeded else
* use `textContent` instead of `innerHTML`
* cache a few `getElementById` calls
* fix a couple of undefined variables
* various assorted lint tweaks

Signed-off-by: XhmikosR <xhmikosr@gmail.com>

scripts/pi-hole/js/taillog.js

@@ -4,6 +4,7 @@
 *
 *  This file is copyright under the latest version of the EUPL.
 *  Please see LICENSE file for your rights under this license. */
+
 var offset, timer, pre, scrolling = true;
 
 // Check every 200msec for fresh data
@@ -14,13 +15,13 @@ function reloadData(){
     clearTimeout(timer);
     $.getJSON("scripts/pi-hole/php/tailLog.php?offset="+offset, function (data)
     {
-        pre.append(data["lines"]);
+        pre.append(data.lines);
 
-        if(scrolling && offset !== data["offset"]) {
+        if(scrolling && offset !== data.offset) {
             pre.scrollTop(pre[0].scrollHeight);
         }
 
-        offset = data["offset"];
+        offset = data.offset;
     });
 
     timer = setTimeout(reloadData, interval);
@@ -30,7 +31,7 @@ $(function(){
     // Get offset at first loading of page
     $.getJSON("scripts/pi-hole/php/tailLog.php", function (data)
     {
-        offset = data["offset"];
+        offset = data.offset;
     });
     pre = $("#output");
     // Trigger function that looks for new data