Add spec for hiding variables and remove the need for ES6 Symbol

app/assets/javascripts/project_variables.js.es6

@@ -23,9 +23,9 @@
       $btn.attr('data-status', newStatus);
-      $variables = $('.variable-value');
-      for (let variable of $variables) {
+      let $variables = $('.variable-value');
+      $variables.each(function (_, variable) {
         let $variable = $(variable);
         let newText = HIDDEN_VALUE_TEXT;
@@ -34,7 +34,7 @@
         }
         $variable.text(newText);
-      }
+      });
       $btn.text(newAction);
     }

spec/features/variables_spec.rb

@@ -29,6 +29,31 @@ describe 'Project variables', js: true do
     end
   end
+  it 'reveals and hides new variable' do
+    fill_in('variable_key', with: 'key')
+    fill_in('variable_value', with: 'key value')
+    click_button('Add new variable')
+
+    page.within('.variables-table') do
+      expect(page).to have_content('key')
+      expect(page).to have_content('******')
+    end
+
+    click_button('Reveal Values')
+
+    page.within('.variables-table') do
+      expect(page).to have_content('key')
+      expect(page).to have_content('key value')
+    end
+
+    click_button('Hide Values')
+
+    page.within('.variables-table') do
+      expect(page).to have_content('key')
+      expect(page).to have_content('******')
+    end
+  end
+
   it 'deletes variable' do
     page.within('.variables-table') do
       find('.btn-variable-delete').click