diff --git a/modules/core/www/assets/js/loginuserpass.js b/modules/core/www/assets/js/loginuserpass.js
index b61a0911eeddcf6acfaf707dc3e0ac787853cd3a..46d50fc4cefeab39cbe198899d5683a19b790349 100644
--- a/modules/core/www/assets/js/loginuserpass.js
+++ b/modules/core/www/assets/js/loginuserpass.js
@@ -1,8 +1,9 @@
+"use strict";
+
 ready(function () {
-    // your code here
     var button = document.getElementById("submit_button");
     button.onclick = function () {
-        this.innerHTML = button.getAttribute("data-processing");;
+        this.innerHTML = button.getAttribute("data-processing");
         this.disabled = true;
 
         var form = document.getElementById("f");
diff --git a/src/js/bundle.js b/src/js/bundle.js
index 8012d152a9bba5a298b455b1b922df2deaaf2afd..055168c37d696b46522e604acafbe8c9bab8ee15 100644
--- a/src/js/bundle.js
+++ b/src/js/bundle.js
@@ -1,3 +1,5 @@
+"use strict";
+
 import ClipboardJS from "clipboard/dist/clipboard";
 import hljs from  "highlight.js/lib/core";
 import xml from "highlight.js/lib/languages/xml";
diff --git a/src/js/logout/logout.js b/src/js/logout/logout.js
index a1b543486b72ce56437d515f8d73282d7f683ec5..f4f68966e65e49105a59acf5f8502b9488ed5b22 100644
--- a/src/js/logout/logout.js
+++ b/src/js/logout/logout.js
@@ -1,3 +1,5 @@
+"use strict";
+
 /**
  * This class is used for the logout page.
  *
diff --git a/src/js/logout/main.js b/src/js/logout/main.js
index 16c508f9ce3506785070cfada90d71c12f9a7f73..929c535bec29dfd887f419dd99c3466e3d1b79a1 100644
--- a/src/js/logout/main.js
+++ b/src/js/logout/main.js
@@ -1,5 +1,7 @@
+"use strict";
+
 import SimpleSAMLLogout from './logout.js';
 
 $(document).ready(function () {
     new SimpleSAMLLogout($('body').attr('id'));
-});
\ No newline at end of file
+});
diff --git a/src/js/main.js b/src/js/main.js
index 1b8b43f8923597b6194add0365048201a7b1e852..47b5079bef402cfcfbb0f541e62227e941d60c22 100644
--- a/src/js/main.js
+++ b/src/js/main.js
@@ -1,3 +1,5 @@
+"use strict";
+
 import "es5-shim";
 import "es6-shim";
 
diff --git a/src/js/style.js b/src/js/style.js
index 5c5cdfed318cbd97562f2481b975ce5838e76ed2..c4a85a05979ac64e911a68445a7fe73d47dad425 100644
--- a/src/js/style.js
+++ b/src/js/style.js
@@ -1 +1,3 @@
+"use strict";
+
 require('../css/default.scss');