diff --git a/api.js b/api.js
index 90b374e..a3d75f1 100644
--- a/api.js
+++ b/api.js
@@ -7,8 +7,8 @@
  */
 
 //Importing self-written modules.
-var lookup = require('./lookup');
-var schedule = require('./schedule');
+const lookup = require('./lookup');
+const schedule = require('./schedule');
 
 /**
  * Takes the information from the request
@@ -58,8 +58,7 @@ function parse(req, res, next, api) {
  */
 function error(str, res, data) {
   res.set('Content-Type', 'application/json');
-  var error = JSON.stringify({'error' : str, 'data' : data}, null, 2);
-  res.status(400).end(error);
+  res.status(400).end(JSON.stringify({'error' : str, 'data' : data}, null, 2));
   return;
 }
 
@@ -72,8 +71,7 @@ function error(str, res, data) {
  */
 function sendResponse(data, res, disablePretty) {
   res.set('Content-Type', 'application/json');
-  var response = JSON.stringify({'data': data}, null, disablePretty ? 0 : 2);
-  res.status(200).end(response);
+  res.status(200).end(JSON.stringify({'data': data}, null, disablePretty ? 0 : 2));
   return;
 }
 
diff --git a/auth.js b/auth.js
index 0d6530f..35ca18b 100644
--- a/auth.js
+++ b/auth.js
@@ -6,13 +6,13 @@
  */
 
 //Importing first and third-party modules.
-var qs = require('querystring');
-var https = require('socks5-https-client');
+const qs = require('querystring');
+const https = require('socks5-https-client');
 
 //Importing self-written modules.
-var crypt = require('./crypt');
-var config = require('./configuration');
-var lookup = require('./lookup');
+const crypt = require('./crypt');
+const config = require('./configuration');
+const lookup = require('./lookup');
 
 /**
  * Function for starting a login request with the Magister servers.
@@ -21,7 +21,7 @@ var lookup = require('./lookup');
  * @param {Function} callback - Callback function to be called after request.
  */
 function getLogin(username, password, callback) {
-	var login = qs.stringify({
+	let login = qs.stringify({
 		GebruikersNaam : username,
 		Wachtwoord : password
 	});
@@ -52,18 +52,18 @@ function getLogin(username, password, callback) {
  * @param {Function} next - Next function supplied by Express.
  */
 function login(req, res, next) {
-	var _data = '';
+	let _data = '';
 
 	req.on('data', function (data) {
 		_data += data;
 	});
 
 	req.on('end', function () {
-		var loginInformation = qs.parse(_data)
+		let loginInformation = qs.parse(_data)
 
 		getLogin(loginInformation.username, loginInformation.password, function (legit) {
-			var username = crypt.encrypt(loginInformation.username);
-			var password = crypt.encrypt(loginInformation.password);
+			let username = crypt.encrypt(loginInformation.username);
+			let password = crypt.encrypt(loginInformation.password);
 			if (legit) {
 		    res.cookie('username', username);
 		    res.cookie('password', password);
@@ -93,10 +93,10 @@ function logout(req, res) {
  * @param {Function} next - Next function supplied by Express.
  */
 function is(req, res, next) {
-	var cookies = qs.parse((req.headers.cookie || '').replace(/\s/g, ''), ';', '=');
+	let cookies = qs.parse((req.headers.cookie || '').replace(/\s/g, ''), ';', '=');
 	if (!cookies.username || !cookies.password) {next(); return;}
 
-	var username = crypt.decrypt(cookies.username),
+	let username = crypt.decrypt(cookies.username),
 	password = crypt.decrypt(cookies.password);
 
 	getLogin(username, password, function (legit) {
diff --git a/configuration.js b/configuration.js
index b41abdc..ec0aa29 100644
--- a/configuration.js
+++ b/configuration.js
@@ -6,7 +6,7 @@
  */
 
 //Import first-party modules.
-var fs = require('fs');
+const fs = require('fs');
 
 /**
  * Function for the return/creating of a settings file/object.
diff --git a/crypt.js b/crypt.js
index 4b5c4f7..863206e 100644
--- a/crypt.js
+++ b/crypt.js
@@ -6,16 +6,16 @@
  */
 
 //Import first-party modules.
-var crypto = require('crypto');
+const crypto = require('crypto');
 
 //Import self-written modules.
-var config = require('./configuration');
+const config = require('./configuration');
 
-//Set local variables.
-var encoding = 'utf8';
-var cryptEncoding = 'hex';
-var algo = 'aes192';
-var passwd = config().encryptionKey;
+//Set local constants.
+const encoding = 'utf8';
+const cryptEncoding = 'hex';
+const algo = 'aes192';
+const passwd = config().encryptionKey;
 
 /**
  * Function for encrypting a string.
@@ -23,8 +23,8 @@ var passwd = config().encryptionKey;
  * @return {String} encryptArray - Encrypted string.
  */
 function encrypt(str) {
-	var cipher = crypto.createCipher(algo, passwd);
-	var encryptArray = [];
+	let cipher = crypto.createCipher(algo, passwd);
+	let encryptArray = [];
 
 	encryptArray.push(cipher.update(str, encoding, cryptEncoding));
 	encryptArray.push(cipher.final(cryptEncoding));
@@ -38,8 +38,8 @@ function encrypt(str) {
  * @return {String} The decrypted string.
  */
 function decrypt(str) {
-	var decipher = crypto.createDecipher(algo, passwd);
-	var decryptArray = [];
+	let decipher = crypto.createDecipher(algo, passwd);
+	let decryptArray = [];
 
 	try {
 		decryptArray.push(decipher.update(str, cryptEncoding, encoding));
diff --git a/database.js b/database.js
index 8a584a7..e0d77e4 100644
--- a/database.js
+++ b/database.js
@@ -7,10 +7,10 @@
  */
 
 //Import first-party modules.
-var fs = require('fs');
+const fs = require('fs');
 
 //Import self-written modules.
-var config = require('./configuration');
+const config = require('./configuration');
 
 /**
  * Function for using a database interface.
@@ -20,13 +20,13 @@ var config = require('./configuration');
 module.exports = function () {
   if (!config().localDatabase) return require('mongoskin').db('mongodb://' + config().database);
   else {
-    var databases = {
+    let databases = {
       index: new (require('nedb'))({ filename: __dirname + '/resources/databases/index.db', autoload: true})
     };
 
     return {
       'collection': function (collection) {
-          var database = databases[collection];
+          let database = databases[collection];
 
           database.drop = function () {
             fs.writeFileSync(database.filename, '');
diff --git a/lookup.js b/lookup.js
index 0dfb852..97d302b 100644
--- a/lookup.js
+++ b/lookup.js
@@ -6,14 +6,14 @@
  */
 
 //Importing first-party modules.
-var fs = require('fs');
+const fs = require('fs');
 
 //Importing self-written modules.
-var config = require('./configuration');
-var database = require('./database')();
+const config = require('./configuration');
+const database = require('./database')();
 
 //Getting local variables from the configuration file.
-var schoolID = config().schoolID;
+const schoolID = config().schoolID;
 
 /**
  * Function for doing a lookup in the database containing all records
@@ -80,8 +80,8 @@ function handle(req, res, next, databaseEntry) {
  * @param {Function} callback - Callback function needed to return the API call.
  */
 function api(req, callback) {
-  var index = database.collection('index');
-  var query = RegExp(req.query.name, 'i');
+  let index = database.collection('index');
+  let query = RegExp(req.query.name, 'i');
 
   if (!config().localDatabase) {
     index.find({$or : [{id : query}, {name : query}, {first_name : query}, {last_name : query}, {username: query}, {group: query}]}).toArray(function (err, databaseEntry) {
@@ -111,8 +111,8 @@ function api(req, callback) {
  * @param {String} list - The search (group) query given by the user.
  */
 function list(req, res, next, list) {
-  var index = database.collection('index');
-  var query = RegExp(list, 'i');
+  let index = database.collection('index');
+  let query = RegExp(list, 'i');
 
   if (!config().localDatabase) {
     index.find({group: list}).toArray(function (err, databaseEntry) {
@@ -177,7 +177,7 @@ function makeUrl(req, databaseEntry) {
  * @param {String} search - The user supplied search query.
  */
 function easter(search) {
-  var list = JSON.parse(fs.readFileSync(__dirname + '/eastereggs.json'));
+  let list = JSON.parse(fs.readFileSync(__dirname + '/eastereggs.json'));
 
   for (entry of list) {
     if (entry.easter == search.toLowerCase()) return entry;
diff --git a/redirecter.js b/redirecter.js
index ac9d155..88058c1 100644
--- a/redirecter.js
+++ b/redirecter.js
@@ -7,7 +7,7 @@
 
 
 //Import first-party modules.
-var qs = require('querystring');
+const qs = require('querystring');
 
 /**
  * Module for redirecting the user after they did a search query in any of the
@@ -16,15 +16,15 @@ var qs = require('querystring');
  * @param {Object} res - Response object supplied by Express.
  */
 module.exports = function (req, res) {
-  var referer = req.headers.referer.split('/')[3] || 'rooster';
-  var _data = '';
+  let referer = req.headers.referer.split('/')[3] || 'rooster';
+  let _data = '';
 
   req.on('data', function (data) {
     _data += data;
   });
 
   req.on('end', function () {
-    var query = qs.parse(_data);
+    let query = qs.parse(_data);
 
     if (query && query.search != '') {
       query.search = query.search.trim();
diff --git a/schedule.js b/schedule.js
index 87c5bf5..225955d 100644
--- a/schedule.js
+++ b/schedule.js
@@ -7,14 +7,14 @@
  */
 
 //Import first-party modules.
-var url = require('url');
+const url = require('url');
 
 //Import third-party modules.
-var http = require('socks5-http-client');
-var cheerio = require('cheerio');
+const http = require('socks5-http-client');
+const cheerio = require('cheerio');
 
 //Import self-written modules.
-var config = require('./configuration');
+const config = require('./configuration');
 
 /**
  * Function being called by Express when the user requests a schedule.
@@ -35,12 +35,12 @@ function get(req, res, next) {
  * @param {Function} callback - Callback function to return the downloaded information.
  */
 function getSchedule(getUrl, callback) {
-  var options = url.parse(getUrl);
+  let options = url.parse(getUrl);
   options.socksPort = config().torPort;
   options.socksHost = config().torHost;
 
   http.get(options, function (res) {
-    var _download = '';
+    let _download = '';
 
     res.on('data', function (data) {
       _download += data;
@@ -58,9 +58,9 @@ function getSchedule(getUrl, callback) {
  * @return {Array} names - An array populated with the schedule names (basic, week)
  */
 function scheduleNames(page) {
-   var extract = cheerio('table tr td[valign="bottom"] table tr td b, table tr td[valign="bottom"] table tr td a', page).text().split(/\s\s/);
-   var tab = 0;
-   var names = [];
+   let extract = cheerio('table tr td[valign="bottom"] table tr td b, table tr td[valign="bottom"] table tr td a', page).text().split(/\s\s/);
+   let tab = 0;
+   let names = [];
 
    for (element of extract) {
       element != '' ? names.push({
@@ -79,15 +79,15 @@ function scheduleNames(page) {
  * @return {Object} scheduleData - The converted JSON datastructure.
  */
 function toJSON(page) {
-  var result = cheerio('td:nth-child(3) table', page);
-  var names = scheduleNames(page);
-  var isTeacher = cheerio(cheerio(page).find('tr.CoreDark').find('td')[3]).find('a').html() == null;
-  var amountOfDays = cheerio(result).find('tr.AccentDark').find('td').length - 1;
-  var amountOfHours = config().amountOfHours;
+  let result = cheerio('td:nth-child(3) table', page);
+  let names = scheduleNames(page);
+  let isTeacher = cheerio(cheerio(page).find('tr.CoreDark').find('td')[3]).find('a').html() == null;
+  let amountOfDays = cheerio(result).find('tr.AccentDark').find('td').length - 1;
+  let amountOfHours = config().amountOfHours;
 
-  var scheduleData = [];
+  let scheduleData = [];
 
-  var offset = isTeacher ? 5 : 6;
+  let offset = isTeacher ? 5 : 6;
 
   //Looping for amount of days
   for (day = 0; day < amountOfDays; day++) {
@@ -95,13 +95,13 @@ function toJSON(page) {
 
     //Looping for amount of hours
     for (hour = 0; hour < amountOfHours; hour++) {
-      var schedule = cheerio('tr:nth-child('+ (offset + hour) +')', result);
+      let schedule = cheerio('tr:nth-child('+ (offset + hour) +')', result);
 
       //Looping for (optional) specialhours
-      var specialHours = schedule.find('table').eq(day).children().length;
+      let specialHours = schedule.find('table').eq(day).children().length;
       scheduleData[day][hour] = {teacher: [], chamber: [], course: [], changed: []};
       for (subhour = 0; subhour < specialHours; subhour++) {
-         var selectedHour = schedule.find('table').eq(day).find('tr').eq(subhour).find('td');
+         let selectedHour = schedule.find('table').eq(day).find('tr').eq(subhour).find('td');
          //Give the value of the schedule hour to the fitting array.
          scheduleData[day][hour].teacher[subhour] = selectedHour.eq(0).text().replace(/\r|\n/g, '');
          scheduleData[day][hour].chamber[subhour] = selectedHour.eq(2).text();
diff --git a/spider.js b/spider.js
index a257706..d8fa7bb 100644
--- a/spider.js
+++ b/spider.js
@@ -7,25 +7,26 @@
  */
 
 //Import first-party modules.
-var url = require('url');
+const url = require('url');
 
 //Import third-party modules
-var http = require('socks5-http-client');
-var cheerio = require('cheerio');
-var iconv = require('iconv-lite');
+const http = require('socks5-http-client');
+const cheerio = require('cheerio');
+const iconv = require('iconv-lite');
 
 //Import self-written modules.
-var config = require('./configuration');
-var database = require('./database')();
+const config = require('./configuration');
+const database = require('./database')();
 
 //Define local variables.
+const schoolID = config().schoolID;
+
 var scheduletypes = [
   'Klasrooster',
   'Docentrooster',
   'Leerlingrooster',
   'Lokaalrooster'
 ];
-var schoolID = config().schoolID;
 
 /**
  * Function for crawling the schedule site for data such as: students, teachers
@@ -38,13 +39,13 @@ function crawl() {
 
     (function (scheduletype) {
 
-      var options = url.parse('http://roosters5.gepro-osi.nl/roosters/rooster.php?school=' + schoolID + '&type=' + scheduletype);
+      let options = url.parse('http://roosters5.gepro-osi.nl/roosters/rooster.php?school=' + schoolID + '&type=' + scheduletype);
       options.socksPort = config().torPort;
       options.socksHost = config().torHost;
 
       http.get(options, function (res) {
 
-        var _download = {};
+        let _download = {};
         _download.type = scheduletype;
 
         res.on('data', function (data) {
@@ -66,7 +67,7 @@ function crawl() {
  * @param {String} page - A string containing a downloaded schedule page.
  */
 function extract(page) {
-	var array = cheerio('select', page).text().split('\n');
+	let array = cheerio('select', page).text().split('\n');
 	return array.splice(1, array.length - 2);
 }
 
@@ -75,36 +76,36 @@ function extract(page) {
  * @param {String} page - A string containing a downloaded schedule page.
  */
 function rip(page) {
-  var list = extract(page.data);
-  var collection = database.collection('index');
+  let list = extract(page.data);
+  let collection = database.collection('index');
 
   if (page.type == 'Leerlingrooster') {
 
     for(studentcategory of list) {
 
       (function (studentcategory) {
-        var options = url.parse('http://roosters5.gepro-osi.nl/roosters/rooster.php?school=' + schoolID + '&type=' + page.type + '&afdeling=' + studentcategory);
+        let options = url.parse('http://roosters5.gepro-osi.nl/roosters/rooster.php?school=' + schoolID + '&type=' + page.type + '&afdeling=' + studentcategory);
         options.socksPort = config().torPort;
         options.socksHost = config().torHost;
 
         http.get(options, function (res) {
-          var _download = '';
+          let _download = '';
 
           res.on('data', function (data) {
             _download += iconv.decode(data, 'binary');
           });
 
           res.on('end', function () {
-            var listOfStudents = cheerio('select', _download).children();
+            let listOfStudents = cheerio('select', _download).children();
 
             for (student in listOfStudents) {
 
               if (!isNaN(student)) {
-                var name = cheerio(listOfStudents[student]).text().split(' - ')[1];
-                var group = cheerio(listOfStudents[student]).text().split(' - ')[0];
-                var id = cheerio(listOfStudents[student]).val();
+                let name = cheerio(listOfStudents[student]).text().split(' - ')[1];
+                let group = cheerio(listOfStudents[student]).text().split(' - ')[0];
+                let id = cheerio(listOfStudents[student]).val();
 
-                var databaseEntry = {
+                let databaseEntry = {
                   'id' : id,
                   'group' : group,
                   'username' : id + name.split(' ')[0].toLowerCase(),
@@ -132,7 +133,7 @@ function rip(page) {
   }
   else {
     for (entry of list) {
-      var databaseEntry = {
+      let databaseEntry = {
         'name' : entry,
         'type' : page.type.replace(/rooster/g, '').toLowerCase()
       }
diff --git a/time.js b/time.js
index 3c6aeac..19aacf1 100644
--- a/time.js
+++ b/time.js
@@ -8,14 +8,14 @@
  */
 
 //Importing self-written modules.
-var config = require('./configuration');
+const config = require('./configuration');
 
 /**
  * Function for getting the time, with minutes as a fracture.
  * @return {Float} time - The time, fractured (20.5 instead of 20:30)
  */
 function get() {
- var time = new Date();
+ let time = new Date();
  return time.getHours() + (time.getMinutes() / 60);
 }
 
@@ -25,8 +25,8 @@ function get() {
  * @return {Array} array - An array containing the time string split in two.
  */
 function parse(timestr) {
-  var parsed = timestr.match(/\d{1,2}:\d+/g);
-  var array = [];
+  let parsed = timestr.match(/\d{1,2}:\d+/g);
+  let array = [];
 
   for (time of parsed) {
     array.push(parseInt(time.split(':')[0]) + (parseInt(time.split(':')[1]) / 60));
@@ -51,8 +51,8 @@ function withinTimespan(timespan) {
   * @return {Boolean} - Returns true if the current time is within the timespan or false when it's not.
  */
 function duringSchool() {
-  var start = parse(config().times[0])[0];
-  var end = parse(config().times[config().times.length - 1])[1];
+  let start = parse(config().times[0])[0];
+  let end = parse(config().times[config().times.length - 1])[1];
 
   if (get() > start && get() < end) return true;
   else return false;
diff --git a/web.js b/web.js
index 2d162aa..8731dd9 100644
--- a/web.js
+++ b/web.js
@@ -7,21 +7,21 @@
  */
 
 //Import first-party modules.
-var fs = require('fs');
+const fs = require('fs');
 
 //Import third-party modules.
-var express = require('express');
-var less = require('express-less');
-var body_parser = require('body-parser');
+const express = require('express');
+const less = require('express-less');
+const body_parser = require('body-parser');
 
 //Import self-written modules.
-var api = require('./api');
-var config = require('./configuration');
-var lookup = require('./lookup');
-var schedule = require('./schedule');
-var auth = require('./auth');
-var redirecter = require('./redirecter');
-var time = require('./time');
+const api = require('./api');
+const config = require('./configuration');
+const lookup = require('./lookup');
+const schedule = require('./schedule');
+const auth = require('./auth');
+const redirecter = require('./redirecter');
+const time = require('./time');
 
 //Setting local variables.
 var app = express();
@@ -83,9 +83,9 @@ function plugins() {
   var pluginsDirectory = fs.readdirSync(__dirname + '/plugins');
 
   for (plugin of pluginsDirectory) {
-    var app = __dirname + '/plugins/' + plugin + '/app.js';
+    let app = __dirname + '/plugins/' + plugin + '/app.js';
     if (fs.existsSync(app)) {
-      var app = require(app)(config().webPort + (1 + pluginsDirectory.indexOf(plugin)), config().webHost);
+      let app = require(app)(config().webPort + (1 + pluginsDirectory.indexOf(plugin)), config().webHost);
     }
   }
 }