Add js or no-js class to html tag.

opentech/static_src/src/javascript/main.js

@@ -104,8 +104,8 @@
         }
     };
 
-    // remove no-js class if js is enabled
-    document.querySelector('html').classList.remove('no-js');
+    // Replace no-js with js class if js is enabled.
+    document.querySelector('html').classList.replace('no-js', 'js');
 
     $(MobileMenu.selector()).each((index, el) => {
         new MobileMenu($(el), $('.js-mobile-menu-close'), $('.header__menus--mobile'), $('.header__search'));

opentech/static_src/src/sass/apply/base/_base.scss

@@ -80,6 +80,20 @@ ol {
     display: none;
 }
 
+.js-hidden,
+%js-hidden {
+    html.js & {
+        @extend %is-hidden;
+    }
+}
+
+.no-js-hidden,
+%no-js-hidden {
+    html.nojs & {
+        @extend %is-hidden;
+    }
+}
+
 .is-unhidden,
 %is-unhidden {
     display: block;

opentech/static_src/src/sass/public/base/_base.scss

@@ -74,11 +74,26 @@ ol {
     transition: opacity, z-index, $transition;
 }
 
+.hidden,
 .is-hidden,
 %is-hidden {
     display: none;
 }
 
+.js-hidden,
+%js-hidden {
+    html.js & {
+        @extend %is-hidden;
+    }
+}
+
+.no-js-hidden,
+%no-js-hidden {
+    html.nojs & {
+        @extend %is-hidden;
+    }
+}
+
 .is-unhidden,
 %is-unhidden {
     display: block;