diff --git a/06/index.js b/06/index.js
index dd00e9f..2ea0118 100644
--- a/06/index.js
+++ b/06/index.js
@@ -4,7 +4,7 @@ filter(process.argv[2], process.argv[3], (error,data) => {
   if(error)
     return console.error('Error: '+error);
 
-  for (var i = 0; i < data.length; i++) {
+  for (let i = 0; i < data.length; i++) {
     console.log(data[i]);
   }
 });
diff --git a/06/modules/filter.js b/06/modules/filter.js
index 0e1f6aa..4357df0 100644
--- a/06/modules/filter.js
+++ b/06/modules/filter.js
@@ -1,5 +1,5 @@
-var fs = require('fs');
-var path = require('path');
+const fs = require('fs');
+const path = require('path');
 
 module.exports = (dir, ext, callback) => {
 
diff --git a/07/index.js b/07/index.js
index f756263..f65060d 100644
--- a/07/index.js
+++ b/07/index.js
@@ -1,6 +1,6 @@
-var http = require('http');
+const http = require('http');
 
-http.get(process.argv[2], (res) =>{
+http.get(process.argv[2], (res) => {
   res.setEncoding('utf8');
   res.on('data', console.log);
   res.on('error', console.error);
diff --git a/08/blindex.js b/08/blindex.js
index 6528cdc..a566f80 100644
--- a/08/blindex.js
+++ b/08/blindex.js
@@ -1,13 +1,13 @@
-var http = require('http');
-var bl = require('bl');
+const http = require('http');
+const bl = require('bl');
 
-http.get(process.argv[2], (res) =>{
+http.get(process.argv[2], (res) => {
   res.pipe(bl( (err,data) => {
     if(err)
       console.error('Error: '+err);
 
-    var string = data.toString();
+    const string = data.toString();
     console.log(string.length);
     console.log(string);
-  } ));
+  }));
 });
diff --git a/08/index.js b/08/index.js
index 05fb3ca..3597ca4 100644
--- a/08/index.js
+++ b/08/index.js
@@ -1,6 +1,6 @@
-var http = require('http');
+const http = require('http');
 
-var string = '';
+const string = '';
 
 http.get(process.argv[2], (res) =>{
   res.setEncoding('utf8');
@@ -8,7 +8,7 @@ http.get(process.argv[2], (res) =>{
     string += data;
   });
 
-  res.on('end', (end) =>{
+  res.on('end', (end) => {
     console.log(string.length);
     console.log(string);
   });
diff --git a/09/afterTest.js b/09/afterTest.js
index e7e0b78..9a276e2 100644
--- a/09/afterTest.js
+++ b/09/afterTest.js
@@ -1,18 +1,17 @@
-var http = require('http');
-var bl = require('bl');
-var after = require("after")
-    , next = after(3, printResults);
+const http = require('http');
+const bl = require('bl');
+const after = require("after"), next = after(3, printResults);
 
-var results = [];
+let results = [];
 
 function printResults(){
-  for (var i = 0; i < results.length; i++) {
+  for (let i = 0; i < results.length; i++) {
     console.log(results[i]);
   }
 }
 
 function get(index) {
-  http.get(process.argv[2+index], (res) =>{
+  http.get(process.argv[2+index], (res) => {
     res.pipe(bl( (err,data) => {
       if(err)
         console.error('Error: '+err);
@@ -25,5 +24,5 @@ function get(index) {
 }
 
 
-for (var i = 0; i < 3; i++)
+for (let i = 0; i < 3; i++)
   get(i);
diff --git a/09/asyncTest.js b/09/asyncTest.js
index 0f512b2..5cc647c 100644
--- a/09/asyncTest.js
+++ b/09/asyncTest.js
@@ -1,15 +1,15 @@
-var http = require('http');
-var bl = require('bl');
-var async = require('async');
+const http = require('http');
+const bl = require('bl');
+const async = require('async');
 
 function printResults(results){
-  for (var i = 0; i < results.length; i++) {
+  for (let i = 0; i < results.length; i++) {
     console.log(results[i]);
   }
 }
 
 function getAsync(url, callback) {
-  http.get(url, (res) =>{
+  http.get(url, (res) => {
     res.pipe(bl( (err,data) => {
       if(err)
         callback(err);
@@ -30,7 +30,7 @@ async.map(process.argv.slice(2,5),getAsync, (error, results) =>{
 //   (callback) => {
 //     get(0, callback);
 //   },
-// ], (error,results)=>{
+// ], (error,results)=> {
 //
 //   if(error)
 //     console.error('Error: '+error);
diff --git a/09/index.js b/09/index.js
index 05c1a3f..fc8e30d 100644
--- a/09/index.js
+++ b/09/index.js
@@ -1,17 +1,17 @@
-var http = require('http');
-var bl = require('bl');
+const http = require('http');
+const bl = require('bl');
 
-var results = [];
-var count = 0;
+let results = [];
+let count = 0;
 
 function printResults(){
-  for (var i = 0; i < results.length; i++) {
+  for (let i = 0; i < results.length; i++) {
     console.log(results[i]);
   }
 }
 
 function get(index) {
-  http.get(process.argv[2+index], (res) =>{
+  http.get(process.argv[2+index], (res) => {
     res.pipe(bl( (err,data) => {
       if(err)
         console.error('Error: '+err);
@@ -27,5 +27,5 @@ function get(index) {
 }
 
 
-for (var i = 0; i < 3; i++)
+for (let i = 0; i < 3; i++)
   get(i);
diff --git a/09/promisesTest.js b/09/promisesTest.js
index d1fde98..6daaf8e 100644
--- a/09/promisesTest.js
+++ b/09/promisesTest.js
@@ -1,8 +1,8 @@
-var http = require('http');
-var bl = require('bl');
+const http = require('http');
+const bl = require('bl');
 
 function printResults(results){
-  for (var i = 0; i < results.length; i++) {
+  for (let i = 0; i < results.length; i++) {
     console.log(results[i]);
   }
 }
@@ -20,7 +20,7 @@ function getPromise(index) {
 }
 
 var arrayPromises = [];
-for (var i = 0; i < 3; i++) {
+for (let i = 0; i < 3; i++) {
   arrayPromises.push( getPromise(i) );
 }
 
diff --git a/10/index.js b/10/index.js
index 1ca414c..9761680 100644
--- a/10/index.js
+++ b/10/index.js
@@ -1,12 +1,12 @@
-var net = require('net');
-var strftime = require('strftime');
+const net = require('net');
+const strftime = require('strftime');
 
 function getDate() {
   // YYYY-MM-DD hh:mm
   return strftime('%Y-%m-%d %H:%M');
 }
 
-var server = net.createServer( (socket) =>{
+const server = net.createServer( (socket) =>{
   socket.end(getDate()+"\n");
 } );
 
diff --git a/11/index.js b/11/index.js
index 9d1dd27..28adce5 100644
--- a/11/index.js
+++ b/11/index.js
@@ -1,7 +1,7 @@
-var http = require('http');
-var fs = require('fs');
+const http = require('http');
+const fs = require('fs');
 
-var server = http.createServer( (req,res) =>{
+const server = http.createServer( (req,res) =>{
   res.writeHead(200, { 'content-type' : 'text-plain' });
   fs.createReadStream(process.argv[3]).pipe(res);
 });
diff --git a/12/index.js b/12/index.js
index 8a7682c..fa74aae 100644
--- a/12/index.js
+++ b/12/index.js
@@ -1,7 +1,7 @@
-var http = require('http');
-var map = require('through2-map');
+const http = require('http');
+const map = require('through2-map');
 
-var server = http.createServer( (req,res) =>{
+const server = http.createServer( (req,res) =>{
   if(req.method !== 'POST')
     return res.end('Only POST please');
 
diff --git a/13/index.js b/13/index.js
index 8fc4eb6..7380e82 100644
--- a/13/index.js
+++ b/13/index.js
@@ -1,10 +1,10 @@
-var http = require('http');
-var url = require('url');
+const http = require('http');
+const url = require('url');
 
-var server = http.createServer( (req,res) =>{
-  var parse = url.parse(req.url, true);
-  var date = new Date(parse.query.iso);
-  var result;
+const server = http.createServer( (req,res) =>{
+  let parse = url.parse(req.url, true);
+  let date = new Date(parse.query.iso);
+  let result;
 
   switch (parse.pathname) {
     case '/api/parsetime':