Fixed keyboard focus remains within modal simulated dialogs.

ECOM-4188
ECOM-5303

lms/static/js/dialog_tab_controls.js

@@ -0,0 +1,73 @@
+var DialogTabControls = (function() {
+    'use strict';
+
+    var focusableChildren,
+        numElements,
+        currentIndex,
+        focusableElementSelectors = 'a, input[type=text], input[type=submit], select, textarea, button',
+        setCurrentIndex = function(currentElement) {
+            var elementIndex = focusableChildren.index(currentElement);
+            if (elementIndex >= 0) {
+                currentIndex = elementIndex;
+            }
+        },
+        initializeTabKeyValues = function(elementName, $closeButton) {
+            focusableChildren = $(elementName).find(focusableElementSelectors);
+            if ($closeButton) {
+                focusableChildren = focusableChildren.add($closeButton);
+            }
+            numElements = focusableChildren.length;
+            currentIndex = 0;
+            focusableChildren[currentIndex].focus();
+            focusableChildren.on('click', function() {
+                setCurrentIndex(this);
+            });
+        },
+        focusElement = function() {
+            var focusableElement = focusableChildren[currentIndex];
+            if (focusableElement) {
+                focusableElement.focus();
+            }
+        },
+        focusPrevious = function() {
+            currentIndex--;
+            if (currentIndex < 0) {
+                currentIndex = numElements - 1;
+            }
+
+            focusElement();
+        },
+        focusNext = function() {
+            currentIndex++;
+            if (currentIndex >= numElements) {
+                currentIndex = 0;
+            }
+
+            focusElement();
+        },
+        setKeydownListener = function($element, $closeButton) {
+            $element.on('keydown', function(e) {
+                var keyCode = e.keyCode || e.which,
+                    escapeKeyCode = 27,
+                    tabKeyCode = 9;
+                if (keyCode === escapeKeyCode) {
+                    e.preventDefault();
+                    if ($closeButton) {
+                        $closeButton.click();
+                    }
+                }
+                if (keyCode === tabKeyCode && e.shiftKey) {
+                    e.preventDefault();
+                    focusPrevious();
+                } else if (keyCode === tabKeyCode) {
+                    e.preventDefault();
+                    focusNext();
+                }
+            });
+        };
+
+    return {
+        initializeTabKeyValues: initializeTabKeyValues,
+        setKeydownListener: setKeydownListener
+    };
+}());