keep focus on modal if no tabbable elements are within it

add a test case

Author: everdimension

lib/helpers/scopeTab.js

@@ -2,7 +2,10 @@ var findTabbable = require('../helpers/tabbable');
 
 module.exports = function(node, event) {
   var tabbable = findTabbable(node);
-  if (!tabbable.length) return;
+  if (!tabbable.length) {
+      event.preventDefault();
+      return;
+  }
   var finalTabbable = tabbable[event.shiftKey ? 0 : tabbable.length - 1];
   var leavingFinalTabbable = (
     finalTabbable === document.activeElement ||

specs/Modal.spec.js

@@ -100,6 +100,19 @@ describe('Modal', function () {
     unmountModal();
   });
 
+  it('keeps focus inside the modal when child has no tabbable elements', function() {
+    var tabPrevented = false;
+    var modal = renderModal({isOpen: true}, 'hello');
+    strictEqual(document.activeElement, modal.portal.refs.content);
+    Simulate.keyDown(modal.portal.refs.content, {
+        key: "Tab",
+        keyCode: 9,
+        which: 9,
+        preventDefault: function() { tabPrevented = true; }
+    });
+    equal(tabPrevented, true);
+  });
+
   it('supports custom className', function() {
     var modal = renderModal({isOpen: true, className: 'myClass'});
     equal(modal.portal.refs.content.className.contains('myClass'), true);