1 files changed, 40 insertions, 0 deletions
diff --git a/ui/safe-active-element.js b/ui/safe-active-element.js
new file mode 100644
index 000000000..4d04add5f
--- /dev/null
+++ b/ui/safe-active-element.js
@@ -0,0 +1,40 @@
+( function( factory ) {
+	if ( typeof define === "function" && define.amd ) {
+
+		// AMD. Register as an anonymous module.
+		define( [ "jquery", "./version" ], factory );
+	} else {
+
+		// Browser globals
+		factory( jQuery );
+	}
+} ( function( $ ) {
+return $.ui.safeActiveElement = function( document ) {
+	var activeElement;
+
+	// Support: IE 9 only
+	// IE9 throws an "Unspecified error" accessing document.activeElement from an <iframe>
+	try {
+		activeElement = document.activeElement;
+	} catch ( error ) {
+		activeElement = document.body;
+	}
+
+	// Support: IE 9 - 11 only
+	// IE may return null instead of an element
+	// Interestingly, this only seems to occur when NOT in an iframe
+	if ( !activeElement ) {
+		activeElement = document.body;
+	}
+
+	// Support: IE 11 only
+	// IE11 returns a seemingly empty object in some cases when accessing
+	// document.activeElement from an <iframe>
+	if ( !activeElement.nodeName ) {
+		activeElement = document.body;
+	}
+
+	return activeElement;
+};
+
+} ) );