Added zIndex method. Fixes #4709 - Add zIndex setter/getter method.

Author: scottgonzalez

tests/unit/core/core.html

@@ -93,6 +93,11 @@
 	</div>
 
 	<div id="aria"></div>
+	
+	<div id="zIndex100" style="z-index: 100;">
+		<div id="zIndexAutoWithParent"></div>
+	</div>
+	<div id="zIndexAutoNoParent"></div>
 </div>
 
 </body>

tests/unit/core/core.js

@@ -48,4 +48,13 @@ test('focus', function() {
 	other.focus();
 });
 
+test('zIndex', function() {
+	var el = $('#zIndexAutoWithParent');
+	equals(el.zIndex(), 100, 'zIndex traverses up to find value');
+	equals(el.zIndex(200), el, 'zIndex setter is chainable');
+	equals(el.zIndex(), 200, 'zIndex setter changed zIndex');
+	
+	equals($('#zIndexAutoNoParent').zIndex(), 0, 'zIndex never explicitly set in hierarchy');
+});
+
 })(jQuery);

ui/ui.core.js

@@ -184,6 +184,26 @@ $.fn.extend({
 		}
 
 		return (/fixed/).test(this.css('position')) || !scrollParent.length ? $(document) : scrollParent;
+	},
+
+	zIndex: function(zIndex) {
+		if (zIndex !== undefined) {
+			return this.css('zIndex', zIndex);
+		}
+
+		var elem = this[0];
+		while (elem && elem.style) {
+			// IE returns 0 when zIndex is not specified
+			// other browsers return an empty string
+			// we ignore the case of nested elements with an explicit value of 0
+			// <div style="z-index: -10;"><div style="z-index: 0;"></div></div>
+			if (elem.style.zIndex !== '' && elem.style.zIndex !== 0) {
+				return +elem.style.zIndex;
+			}
+			elem = elem.parentNode;
+		}
+
+		return 0;
 	}
 });