refactoring and if for frontend/backend check added

app.js

-var express    = require('express');
-var bodyParser = require('body-parser');
+const express    = require('express');
+const bodyParser = require('body-parser');
 
-var exec       = require('child_process').exec;
-var execSync   = require('child_process').execSync;
-var fs         = require('fs');
-var path       = require('path');
-var fsReaddir = require('fs-readdir');
-var JSZip = require('jszip');
+const exec       = require('child_process').exec;
+const execSync   = require('child_process').execSync;
+const fs         = require('fs');
+const path       = require('path');
+const fsReaddir = require('fs-readdir');
+const JSZip = require('jszip');
 
-var exphbs = require('express-handlebars');
+const exphbs = require('express-handlebars');
 // global.jQuery = require('jquery');
 // const bootstrap = require('bootstrap');
 //initializer
-var initGitRepos = require('./initializers/gitRepos.js');
+const initGitRepos = require('./initializers/gitRepos.js');
 //load names of available download files
 const downloadFiles = require('./downloadFiles.json');
 const downloadNames = Object.keys(downloadFiles);
 
 //load functions for frontend and backend build
-let backendFunctions = require('./backendFunctions.js');
-let frontendFunctions = require('./frontendFunctions.js');
-let zipFunctions = require('./zipFunctions.js');
+const backendFunctions = require('./backendFunctions.js');
+const frontendFunctions = require('./frontendFunctions.js');
+const zipFunctions = require('./zipFunctions.js');
 
-var app = express();
+const app = express();
 
 app.use(bodyParser.urlencoded({
 	extended: true
@@ -66,6 +66,13 @@ app.use(bodyParser.json());
 		backendChecked = checkedFiles.find(function(file){
 			return file === 'explorviz-ui-backend';
 		});
+		frontendChecked = checkedFiles.find(function(file){
+			return file === 'explorviz-ui-frontend';
+		});
+
+		if(!(backendChecked || frontendChecked)){
+			res.render('home', {downloadFiles: downloadNames});
+		}
 
 		if (backendChecked){
 
@@ -92,9 +99,7 @@ app.use(bodyParser.json());
 
 		} 
 
-		frontendChecked = checkedFiles.find(function(file){
-			return file === 'explorviz-ui-frontend';
-		});
+		
 
 		if (frontendChecked){
 			const fileName = frontendChecked;