$.maxZ

jquery.maxz.js

// inspired by:
// http://snipplr.com/view.php?codeview&id=15214
(function ($) {
  
  $.maxZ = function () {
    var $all = $("body > *");
    
    return Math.max.apply(Math, $.map($all, function (el) {
      var $el = $(el);
      var z = 0;
      
      if ($el.css("position") !== "static") {
        z = parseInt($el.css("z-index"), 10) || 1;
      }
        
      return z;
    }));
  };
  
}(jQuery));
                          
// console.log($.maxZ());