Array.Min, Array.Max and jQuery.map()

jQueryMap.html

<span id="toolbar">
    <a title="Link 1" tabindex="-1" href="#"></a>
    <a title="Link 1" tabindex="-2" href="#"></a>
</span>

jqueryMap.js

$(function() {
    //Thanks to John Resig - http://ejohn.org/blog/fast-javascript-maxmin/
    Array.max = function(array) {
        return Math.max.apply(Math, array);
    };
    Array.min = function(array) {
        return Math.min.apply(Math, array);
    };

    // Doing some map and find
    //var topToolBar = $(top.document).find('#toolbar');
    var someToolBar = $('#toolbar');
    var tabIndexArrayObject = someToolBar.find('a').map(function() {
        return this.tabIndex;
    });
    var tabIndexArray = Array.prototype.slice.call(tabIndexArrayObject.get());
    var tabIndex = Array.min(tabIndexArray) - 1;
    alert(tabIndex);
});