Change codes with EC6 Syntax

-var express = require('express');
-var app = express();
-var bodyParser = require('body-parser');
+let express = require('express');
+let app = express();
+let bodyParser = require('body-parser');
 
 app.use(bodyParser.urlencoded({ extended: false }));
 app.use(bodyParser.json());
 
 
-var books = new Array();
+let books = new Array();
 
-app.get('/books/:bookId', function (req, res) {
-	var bookId = req.params.bookId;
+app.get('/books/:bookId', (req, res) => {
+	let bookId = req.params.bookId;
     console.log(books[bookId]);
     res.send(books[bookId]);
 });
@@ -23,21 +23,21 @@ app.get('/books/:bookId', function (req, res) {
 	"author" : "jin"
 }
 */
-app.post('/books', function (req, res) {
+app.post('/books', (req, res) => {
 	// Create book information
 	books[req.body.id] = [req.body.id, req.body.name, req.body.price, req.body.author];
 	res.send(books[req.body.id]);
 })
 
-app.put('/books', function (req, res) {
+app.put('/books', (req, res) => {
 	// Update book information
 
 })
 
 
-app.delete('/books/:bookId', function (req, res) {
+app.delete('/books/:bookId', (req, res) => {
 	// Delete book information
 
 })
-var server = app.listen(80);
+let server = app.listen(80);
 	console.log(books);

-var express = require('express');
-var app = express();
-var bodyParser = require('body-parser');
-var session = require('express-session')
+let express = require('express');
+let app = express();
+let bodyParser = require('body-parser');
+let session = require('express-session')
 
 app.use(session({ secret: 'keyboard cat', cookie: { maxAge: 60000 }}))
 app.use(bodyParser.urlencoded({ extended: false }));
 app.use(bodyParser.json());
 
 
-var users = new Array();
+let users = new Array();
 users[0] = {
 	"userId" : 0,
 	"name" : "jin",
@@ -16,7 +16,7 @@ users[0] = {
 	"isAdmin" : true
 }
 
-app.put('/login', function (req, res) {
+app.put('/login', (req, res) => {
 	// users 배열에서 찾도록 처리 해야 함
 	// admin 여부를 확인하여 체크
 	// req.body.id : ID
@@ -25,7 +25,7 @@ app.put('/login', function (req, res) {
 	res.send("Login");
 });
 
-app.put('/logout', function (req, res) {
+app.put('/logout', (req, res) => {
 	// Logout
 	// 세션 유효 여부를 체크하고 세션 Delete
 	req.session.userId = null;
@@ -33,7 +33,7 @@ app.put('/logout', function (req, res) {
 
 });
 
-var auth = function (req, res, next) {
+let auth = (req, res, next) => {
 	// Session Check
 	// 어드민 여부 체크 필요
 	if (req.session.userId != null)
@@ -42,11 +42,11 @@ var auth = function (req, res, next) {
 		res.send("Error");
 
 };
-app.get('/user/:userId', auth,function (req, res) {
+app.get('/user/:userId', auth, (req, res) => {
 	// get User Information
 	res.send("OK");
 });
 
 // 사용자 추가 시에 admin 여부도 추가해야 함
 
-var server = app.listen(80);
+let server = app.listen(80);