How to find the highest z-index using jQuery

Question

I have a number of div elements with different z-index. And I want to find the highest z-index among these divs - how can I achieve it?

CSS:

#layer-1         


        

Answer 1

This is taken directly from jquery-ui, it works really well:

(function ($) {
  $.fn.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;
    }
})(jQuery);

Answer 2

If you are doing what I think you're doing, there is no need. Just do this:

$('div[id^=layer-]').css('z-index', 0);
$(this).css('z-index', 1000);

Answer 3

This would do it:

$(document).ready(function() {
    var array = [];
    $("div").each(function() {
        array.push($(this).css("z-index"));
    });
    var index_highest = Math.max.apply(Math, array);
    alert(index_highest);
});

Try this

Answer 4

Try my fiddle:

http://planitize.tumblr.com/post/23541747264/get-highest-z-index-with-descendants-included

This combines three advantages I haven't seen combined elsewhere:

• Gets either the highest explicitly defined z-index (default) or the highest computed one.
• Will look at all descendants of your selector, or all descendants of the document if none is supplied.
• Will return either the value of the highest z, or the element that has the highest z.

One disadvantage: no cross-browser guarantees.

Answer 5

Try this :

var index_highest = 0;
$('div').each(function(){
    var index_current = parseInt($(this).css("z-index"), 10);
    if(index_current > index_highest) {
        index_highest = index_current;
    }
}); 

Answer 6

Note that z-index only affects positioned elements. Therefore, any element with position: static will not have a z-index, even if you assign it a value. This is especially true in browsers like Google Chrome.

var index_highest = 0;   
// more effective to have a class for the div you want to search and 
// pass that to your selector
$("#layer-1,#layer-2,#layer-3,#layer-4").each(function() {
    // always use a radix when using parseInt
    var index_current = parseInt($(this).css("zIndex"), 10);
    if(index_current > index_highest) {
        index_highest = index_current;
    }
});

JSFiddle demo

A general jQuery selector like that when used with an option that returns one value will merely return the first So your result is simply the z-index of the first div that jQuery grabs. To grab only the divs you want, use a class on them. If you want all divs, stick with div.