Add "contains" module

src/api.js

@@ -28,6 +28,7 @@ if (typeof selector !== 'undefined') {
     api.find = selector.find;
 }
 
+module contains from './contains'; extend($, contains);
 module mode from './mode'; extend($, mode);
 module noconflict from './noconflict'; extend($, noconflict);
 module type from './type'; extend($, type);

src/contains.js

@@ -0,0 +1,32 @@
+/**
+ * @module contains
+ */
+
+/**
+ * Test whether an element contains another element in the DOM.
+ *
+ * @param {Element} container The element that may contain the other element.
+ * @param {Element} element The element that may be a descendant of the other element.
+ * @return {Boolean} Whether the `container` element contains the `element`.
+ * @example
+ *     $.contains(parentElement, childElement);
+ *     ➤ true/false
+ */
+
+function contains(container, element) {
+    if(!container || !element || container === element) {
+        return false;
+    } else if (container.contains) {
+        return container.contains(element);
+    } else if (container.compareDocumentPosition) {
+        return !(container.compareDocumentPosition(element) & Node.DOCUMENT_POSITION_DISCONNECTED);
+    }
+    return false;
+}
+
+
+/*
+ * Export interface
+ */
+
+export { contains };

src/event.js

@@ -218,13 +218,7 @@ function isAttachedToDocument(element) {
     if (element === window || element === document) {
         return true;
     }
-    var container = element.ownerDocument.documentElement;
-    if (container.contains) {
-        return container.contains(element);
-    } else if (container.compareDocumentPosition) {
-        return !(container.compareDocumentPosition(element) & Node.DOCUMENT_POSITION_DISCONNECTED);
-    }
-    return false;
+    return $.contains(element.ownerDocument.documentElement, element);
 }
 
 /**

test/index.html

@@ -46,6 +46,7 @@
         <script src="spec/array.js"></script>
         <script src="spec/attr.js"></script>
         <script src="spec/class.js"></script>
+        <script src="spec/contains.js"></script>
         <script src="spec/css.js"></script>
         <script src="spec/data.js"></script>
         <script src="spec/dom.js"></script>

test/spec/contains.js

@@ -0,0 +1,26 @@
+describe('contains', function() {
+
+    it('should recognize descendant element is contained by other element', function() {
+        var container = document,
+            element = $('#testFragment')[0];
+        expect($.contains(container, element)).to.be.true;
+    });
+
+    it('should recognize descendant element is contained by other element (within detached fragment)', function() {
+        var container = $('<div><span></span></div>'),
+            element = container.find('span')[0];
+        expect($.contains(container[0], element)).to.be.true;
+    });
+
+    it('should recognize ancestor element is not contained by other element', function() {
+        var container = document,
+            element = $('#testFragment')[0];
+        expect($.contains(element, container)).to.be.false;
+    });
+
+    it('should recognize element is not contained by itself', function() {
+        var element = $('#testFragment')[0];
+        expect($.contains(element, element)).to.be.false;
+    });
+
+});