diff --git a/examples/demo.js b/examples/demo.js
index ad512bb9..731b8603 100644
--- a/examples/demo.js
+++ b/examples/demo.js
@@ -2,7 +2,7 @@ document.addEventListener('DOMContentLoaded', function () {
           
     /*Scroll to top when arrow up clicked BEGIN*/
     $(window).scroll(function() {
-        var height = $(window).scrollTop();
+        let height = $(window).scrollTop();
         if (height > 100) {
             $('#back2Top').fadeIn();
         } else {
@@ -28,16 +28,16 @@ document.addEventListener('DOMContentLoaded', function () {
         e.preventDefault();
     })
 
-    var toolbox;
+    let toolbox;
   
     (function() {
   
-        var org = urlHash().getUrlHashParameter('o') || 'publiclab';
-        var repo = urlHash().getUrlHashParameter('r') || 'plots2';
-        var ftoLabel = urlHash().getUrlHashParameter('f') || 'first-timers-only';
-        var candidateLabel = urlHash().getUrlHashParameter('c') || 'fto-candidate';
-        var recencyLabel = urlHash().getUrlHashParameter('l') || 'week';
-        var leaderboardState = urlHash().getUrlHashParameter('s') || 'week';
+        let org = urlHash().getUrlHashParameter('o') || 'publiclab';
+        let repo = urlHash().getUrlHashParameter('r') || 'plots2';
+        let ftoLabel = urlHash().getUrlHashParameter('f') || 'first-timers-only';
+        let candidateLabel = urlHash().getUrlHashParameter('c') || 'fto-candidate';
+        let recencyLabel = urlHash().getUrlHashParameter('l') || 'week';
+        let leaderboardState = urlHash().getUrlHashParameter('s') || 'week';
   
         toolbox = CommunityToolbox(org, repo);
         if (repo === 'all') {
diff --git a/examples/themes.js b/examples/themes.js
index fa60c993..7224ff24 100644
--- a/examples/themes.js
+++ b/examples/themes.js
@@ -2,9 +2,9 @@
 //      NIGHT MODE LOGIC
 //===============================================================
   $(document).ready(() => {
-    var body=document.querySelector('body');
-    var toggleButton=document.getElementById('myonoffswitch');
-    var toggle = localStorage.getItem('currentToggle');
+    let body=document.querySelector('body');
+    let toggleButton=document.getElementById('myonoffswitch');
+    let toggle = localStorage.getItem('currentToggle');
 
     // Sets images' theme accordingly when the page is loaded
     setTimeout(()=> {
@@ -105,7 +105,7 @@
     buttonClickCallbackNightTheme = (e) => {
       e.preventDefault();
       setTimeout(() => {
-        var recentContribsSectionImgs = document.getElementsByClassName('recent-contributors')[0].getElementsByTagName("img");
+        let recentContribsSectionImgs = document.getElementsByClassName('recent-contributors')[0].getElementsByTagName("img");
         let check=localStorage.getItem('currentToggle');
         let images = [...recentContribsSectionImgs ];
         if(check==="night") {
diff --git a/examples/urlHash.js b/examples/urlHash.js
index d926c449..f101bc9b 100644
--- a/examples/urlHash.js
+++ b/examples/urlHash.js
@@ -1,16 +1,16 @@
 function urlHash() {
   function getUrlHashParameter(param) {
-    var params = getUrlHashParameters();
+    let params = getUrlHashParameters();
     return params[param];
   
   }
   
   function getUrlHashParameters() {
   
-    var sPageURL = window.location.hash;
+    let sPageURL = window.location.hash;
     if (sPageURL) sPageURL = sPageURL.split('#')[1];
-    var pairs = sPageURL.split('&');
-    var object = {};
+    let pairs = sPageURL.split('&');
+    let object = {};
     pairs.forEach(function(pair, i) {
       pair = pair.split('=');
       if (pair[0] != '') object[pair[0]] = pair[1];
@@ -22,19 +22,19 @@ function urlHash() {
   // and transforms to: url.com#paramName=value&paramName1=value
   function setUrlHashParameters(params) {
   
-    var keys = Object.keys(params);
-    var values = Object.values(params);
-    var pairs = [];
+    let keys = Object.keys(params);
+    let values = Object.values(params);
+    let pairs = [];
     keys.forEach(function(key, i) {
       if (key != '') pairs.push(keys[i] + '=' + values[i]);
     });
-    var hash = pairs.join('&');
+    let hash = pairs.join('&');
     window.location.hash = hash;
   
   }
   
   function setUrlHashParameter(param, value) {
-    var params = getUrlHashParameters();
+    let params = getUrlHashParameters();
     params[param] = value;
     setUrlHashParameters(params);
   
diff --git a/src/UI/contributorsUI.js b/src/UI/contributorsUI.js
index fe0a97da..e1e79da2 100644
--- a/src/UI/contributorsUI.js
+++ b/src/UI/contributorsUI.js
@@ -6,10 +6,10 @@ function insertContributors(AllContributors){
     document.getElementById("spinner-icon").style.display = "none";
   
     let totalContributors = 0;
-    var usernames = AllContributors.map(function getContributorUsername(c) {
+    let usernames = AllContributors.map(function getContributorUsername(c) {
       return `@${c.login}`;
     });
-    var avatars = AllContributors.map(function getContributorAvatarURL(c) {
+    let avatars = AllContributors.map(function getContributorAvatarURL(c) {
       return `<a href="#" title="${c.login}"><img width="100px" src="${c.avatar_url}"></a>`;
     });
     totalContributors += AllContributors.length;
diff --git a/src/UI/issuesUI.js b/src/UI/issuesUI.js
index 4384117a..66dd5f1f 100644
--- a/src/UI/issuesUI.js
+++ b/src/UI/issuesUI.js
@@ -3,7 +3,7 @@ var moment = require('moment');
 
 
 function generateIssueHtml(title, body, githubUrl, repo) {
-    var repoName = githubUrl.split('/')[4],
+    let repoName = githubUrl.split('/')[4],
         repoUrl = githubUrl.split('/').slice(0, 5).join('/'),
         html = '<div class="panel panel-default">\
       <div class="panel-heading">\
@@ -18,7 +18,7 @@ function generateIssueHtml(title, body, githubUrl, repo) {
   }
   
 function insertIssue(issue, el) {
-    var body = "";
+    let body = "";
     body += "<div style='float:right;' class='labels'>"
     issue.labels.forEach(function(label) {
       body += "<a class='label label-default' href='" + label.url + "' style='background:#" + label.color + ";'>" + label.name + "</a> ";
diff --git a/src/scripts/chart.js b/src/scripts/chart.js
index 99bf8304..c9ad7195 100644
--- a/src/scripts/chart.js
+++ b/src/scripts/chart.js
@@ -6,7 +6,7 @@ function generateChart(args) {
   args.label = args.label || "";
   args.title = args.title || "";
 
-  var colors = {
+  let colors = {
     "blue":   "rgb(54, 162, 235)",
     "red":    "rgb(255, 99, 132)",
     "green":  "rgb(75, 192, 192)",
@@ -15,9 +15,9 @@ function generateChart(args) {
     "purple": "rgb(153, 102, 255)",
     "yellow": "rgb(255, 205, 86)"
   }
-  var colorNames = Object.keys(colors);
+  let colorNames = Object.keys(colors);
 
-  var barChartData = {
+  let barChartData = {
     // labels: ["January", "February", "March", "April", "May", "June", "July"],
     datasets: [{
       label: args.label,
@@ -28,8 +28,8 @@ function generateChart(args) {
     }]
   }
 
-  var ctx = document.getElementById("canvas").getContext("2d");
-  var chart = new Chart(ctx, {
+  let ctx = document.getElementById("canvas").getContext("2d");
+  let chart = new Chart(ctx, {
     type: 'bar',
     data: barChartData,
     options: {
diff --git a/src/utils/contribsUtil/fetchAllRepoContribs.js b/src/utils/contribsUtil/fetchAllRepoContribs.js
index 6bbce2a1..11a6fa61 100644
--- a/src/utils/contribsUtil/fetchAllRepoContribs.js
+++ b/src/utils/contribsUtil/fetchAllRepoContribs.js
@@ -11,9 +11,9 @@ function fetchAllRepoContribs(org, repo) {
     return api.Repositories
           .getRepoContributors(org, repo, {method: "HEAD", qs: { sort: 'pushed', direction: 'desc', per_page: 100 } })
           .then(function gotContribData(contribData) {
-            var headers = contribData;
+            let headers = contribData;
             if (headers.hasOwnProperty("link")) {
-              var parsed = parse(headers['link']);
+              let parsed = parse(headers['link']);
               if(parsed.last.page!=undefined) {
                 totalPages = parseInt(parsed.last.page);
               }
@@ -27,7 +27,7 @@ function fetchAllRepoContribs(org, repo) {
             let promises = [];
 
             for(let i = 1; i <= totalPages; i++) {
-              var currentPromise = api.Repositories
+              let currentPromise = api.Repositories
                                   .getRepoContributors(org, repo, { method:"GET", qs: { sort: 'pushed', direction: 'desc', per_page: 100, page:i } })
                                   .then(function gotRepoContributors(contributors) {
                                     if (contributors!=undefined && (contributors != null || contributors.length > 0)) {
diff --git a/src/utils/contribsUtil/storeAllContribsInDb.js b/src/utils/contribsUtil/storeAllContribsInDb.js
index 8ebc0a2b..7311f00a 100644
--- a/src/utils/contribsUtil/storeAllContribsInDb.js
+++ b/src/utils/contribsUtil/storeAllContribsInDb.js
@@ -6,7 +6,7 @@ let model_utils = require('../../models/utils')
 function storeAllContribsInDb(org) {
 	let AllContributors = [];
 	let promises = [];
-	var contributorSet = new Set([]);
+	let contributorSet = new Set([]);
 	return new Promise((resolve, reject) => {
 		model_utils.getItem('allContributors').then((allContributors) => {
 			// If all contributors list is not in the database, it makes a fresh call to Github API
diff --git a/src/utils/getRepoContributors.js b/src/utils/getRepoContributors.js
index 4e1bb606..fd38eb96 100644
--- a/src/utils/getRepoContributors.js
+++ b/src/utils/getRepoContributors.js
@@ -14,11 +14,11 @@ options = {
 // get list of contributors to a repo in a given time frame
 function getRepoContributors(username, repo, options){
     commits = getCommitsInRange(username, repo, options);   
-    var result = [];
-    var lookup = {};
-    for (var i=0; i<commits.length; i++){
-        var item = commits[i]["commit"]["author"]["name"];
-        var name = item;
+    let result = [];
+    let lookup = {};
+    for (let i=0; i<commits.length; i++){
+        let item = commits[i]["commit"]["author"]["name"];
+        let name = item;
         if(!(name in lookup)){
             lookup[name] = 1;
             result.push(name);
@@ -37,7 +37,7 @@ function getCommitsInRange(username, repo, options){
 
 // send GET request
 function httpGet(url){
-    var xmlHttp = new XMLHttpRequest();
+    let xmlHttp = new XMLHttpRequest();
     xmlHttp.open( "GET", url, false ); // false for synchronous request
     xmlHttp.send( null );
     return xmlHttp.responseText;