diff --git a/kallithea/public/js/base.js b/kallithea/public/js/base.js
--- a/kallithea/public/js/base.js
+++ b/kallithea/public/js/base.js
@@ -409,14 +409,13 @@ function ajaxGET(url, success, failure) 
 
 function ajaxPOST(url, postData, success, failure) {
     postData['_session_csrf_secret_token'] = _session_csrf_secret_token;
-    var postData = _toQueryString(postData);
     if(failure === undefined) {
         failure = function(jqXHR, textStatus) {
                 if (textStatus != "abort")
                     alert("Error posting to server: " + textStatus);
             };
     }
-    return $.ajax({url: url, data: postData, type: 'POST', headers: {'X-PARTIAL-XHR': '1'}, cache: false})
+    return $.ajax({url: url, data: _toQueryString(postData), type: 'POST', headers: {'X-PARTIAL-XHR': '1'}, cache: false})
         .done(success)
         .fail(failure);
 }
@@ -443,14 +442,14 @@ function _onSuccessFollow(target){
         $target.removeClass('follow').addClass('following');
         $target.prop('title', _TM['Stop following this repository']);
         if ($f_cnt.html()) {
-            var cnt = Number($f_cnt.html())+1;
+            const cnt = Number($f_cnt.html())+1;
             $f_cnt.html(cnt);
         }
     } else {
         $target.removeClass('following').addClass('follow');
         $target.prop('title', _TM['Start following this repository']);
         if ($f_cnt.html()) {
-            var cnt = Number($f_cnt.html())-1;
+            const cnt = Number($f_cnt.html())-1;
             $f_cnt.html(cnt);
         }
     }
@@ -551,7 +550,6 @@ var q_filter = (function() {
         return _namespace[target];
     };
     return function (target, $nodes, display_element) {
-        var $nodes = $nodes;
         var $q_filter_field = $('#' + target);
         var F = namespace(target);
 
diff --git a/kallithea/public/js/codemirror_loadmode.js b/kallithea/public/js/codemirror_loadmode.js
--- a/kallithea/public/js/codemirror_loadmode.js
+++ b/kallithea/public/js/codemirror_loadmode.js
@@ -10,13 +10,13 @@
     var deps = CodeMirror.modes[mode].dependencies;
     if (!deps) return cont();
     var missing = [];
-    for (var i = 0; i < deps.length; ++i) {
+    for (let i = 0; i < deps.length; ++i) {
       if (!CodeMirror.modes.hasOwnProperty(deps[i]))
         missing.push(deps[i]);
     }
     if (!missing.length) return cont();
     var split = splitCallback(cont, missing.length);
-    for (var i = 0; i < missing.length; ++i)
+    for (let i = 0; i < missing.length; ++i)
       CodeMirror.requireMode(missing[i], split);
   }
 
@@ -62,10 +62,11 @@
 
   CodeMirror.getFilenameAndExt = function(filename){
     var parts = filename.split('.');
+    var ext;
 
     if (parts.length > 1){
-        var ext = parts.pop();
-        var filename = parts.join("");
+        ext = parts.pop();
+        filename = parts.join("");
     }
     return {"filename": filename, "ext": ext};
   };
diff --git a/kallithea/public/js/graph.js b/kallithea/public/js/graph.js
--- a/kallithea/public/js/graph.js
+++ b/kallithea/public/js/graph.js
@@ -82,7 +82,7 @@ function BranchRenderer(canvas_id, conte
 		}
 
 		var lineCount = 1;
-		for (var i=0;i<data.length;i++) {
+		for (let i=0;i<data.length;i++) {
 			var in_l = data[i][1];
 			for (var j in in_l) {
 				var m = in_l[j][0];
@@ -95,7 +95,7 @@ function BranchRenderer(canvas_id, conte
 		var box_size = Math.min(18, (canvasWidth - edge_pad * 2) / lineCount);
 		var base_x = canvasWidth - edge_pad;
 
-		for (var i=0; i < data.length; ++i) {
+		for (let i=0; i < data.length; ++i) {
 			var row = document.getElementById(row_id_prefix+idx);
 			if (row == null) {
 				console.log("error: row "+row_id_prefix+idx+" not found");
@@ -120,7 +120,7 @@ function BranchRenderer(canvas_id, conte
 			var rowY = Math.floor(row.offsetTop + firstincell.offsetTop + firstincell.offsetHeight/2);
 			var nextY = Math.floor((next == null) ? rowY + row.offsetHeight/2 : next.offsetTop + nextFirstincell.offsetTop + nextFirstincell.offsetHeight/2);
 
-			for (var j in in_l) {
+			for (let j in in_l) {
 				const line = in_l[j];
 				const start = line[0];
 				const end = line[1];
@@ -146,7 +146,7 @@ function BranchRenderer(canvas_id, conte
 				}
 
 				if (dead_end) {
-					var gradient = this.ctx.createLinearGradient(x,rowY,x,nextY);
+					let gradient = this.ctx.createLinearGradient(x,rowY,x,nextY);
 					gradient.addColorStop(0,this.calcColor(color, 0.0, 0.65));
 					gradient.addColorStop(1,this.calcColor(color, 1.0, 0.0));
 					this.ctx.strokeStyle = gradient;
@@ -157,7 +157,7 @@ function BranchRenderer(canvas_id, conte
 				// the merged color
 				else if (color != node[1] && start == node[0])
 				{
-					var gradient = this.ctx.createLinearGradient(x,rowY,x,nextY);
+					let gradient = this.ctx.createLinearGradient(x,rowY,x,nextY);
 					gradient.addColorStop(0,this.calcColor(node[1], 0.0, 0.65));
 					gradient.addColorStop(1,this.calcColor(color, 0.0, 0.65));
 					this.ctx.strokeStyle = gradient;
diff --git a/kallithea/templates/summary/statistics.html b/kallithea/templates/summary/statistics.html
--- a/kallithea/templates/summary/statistics.html
+++ b/kallithea/templates/summary/statistics.html
@@ -57,10 +57,10 @@ var total = 0;
 var tbl = document.createElement('table');
 tbl.setAttribute('class','trending_language_tbl');
 var cnt = 0;
-for (var i=0;i<data.length;i++){
+for (let i=0;i<data.length;i++){
     total+= data[i][1].count;
 }
-for (var i=0;i<data.length;i++){
+for (let i=0;i<data.length;i++){
     cnt += 1;
 
     var hide = cnt>2;
@@ -136,13 +136,13 @@ function SummaryPlot(from,to,dataset,ove
             "to":to
         }
     };
-    for(var key in dataset){
-      var data = dataset[key].data;
+    for(let key in dataset){
+      let data = dataset[key].data;
       for(var d in data){
         data[d].time *= 1000;
       }
     }
-    for(var key in overview_dataset){
+    for(let key in overview_dataset){
       overview_dataset[key][0] *= 1000;
     }
     var choiceContainer = $("#legend_choices")[0];
@@ -377,7 +377,7 @@ function SummaryPlot(from,to,dataset,ove
             if (previousPoint != item.datapoint) {
                 previousPoint = item.datapoint;
 
-                var tooltip = $("#tooltip")[0];
+                let tooltip = $("#tooltip")[0];
                 if(tooltip) {
                       tooltip.parentNode.removeChild(tooltip);
                 }
@@ -414,7 +414,7 @@ function SummaryPlot(from,to,dataset,ove
             }
         }
         else {
-              var tooltip = $("#tooltip")[0];
+              let tooltip = $("#tooltip")[0];
 
               if(tooltip) {
                     tooltip.parentNode.removeChild(tooltip);
@@ -427,7 +427,7 @@ function SummaryPlot(from,to,dataset,ove
      * MAIN EXECUTION
      */
 
-    var data = getDataAccordingToRanges(initial_ranges);
+    let data = getDataAccordingToRanges(initial_ranges);
     generateCheckboxes(data);
 
     //main plot
diff --git a/kallithea/templates/summary/summary.html b/kallithea/templates/summary/summary.html
--- a/kallithea/templates/summary/summary.html
+++ b/kallithea/templates/summary/summary.html
@@ -341,10 +341,10 @@ $(document).ready(function(){
     var tbl = document.createElement('table');
     tbl.setAttribute('class','table');
     var cnt = 0;
-    for (var i=0;i<data.length;i++){
+    for (let i=0;i<data.length;i++){
         total+= data[i][1].count;
     }
-    for (var i=0;i<data.length;i++){
+    for (let i=0;i<data.length;i++){
         cnt += 1;
 
         var hide = cnt>2;