z-index.js

/*!
 * zIndex plugin from jQuery UI Core - v1.10.4
 * http://jqueryui.com
 *
 * Copyright 2014 jQuery Foundation and other contributors
 * Released under the MIT license.
 * http://jquery.org/license
 *
 * http://api.jqueryui.com/category/ui-core/
 */
define([
    'jquery'
], function ($, undefined) {

// plugins
    $.fn.extend({
        zIndex: function (zIndex) {
            if (zIndex !== undefined) {
                return this.css("zIndex", zIndex);
            }

            if (this.length) {
                var elem = $(this[0]), position, value;
                while (elem.length && elem[0] !== document) {
                    // Ignore z-index if position is set to a value where z-index is ignored by the browser
                    // This makes behavior of this function consistent across browsers
                    // WebKit always returns auto if the element is positioned
                    position = elem.css("position");
                    if (position === "absolute" || position === "relative" || position === "fixed") {
                        // IE returns 0 when zIndex is not specified
                        // other browsers return a 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>
                        value = parseInt(elem.css("zIndex"), 10);
                        if (!isNaN(value) && value !== 0) {
                            return value;
                        }
                    }
                    elem = elem.parent();
                }
            }

            return 0;
        }
    });
});