jQuery 要素のセット内の最大の z-index 値を見つける方法は?

<code class="javascript">var index_highest = 0;   
// Use a class selector to target specific divs or `div` for all divs
$("#layer-1,#layer-2,#layer-3,#layer-4").each(function() {
    // Use parseInt with radix to handle non-integer string values
    var index_current = parseInt($(this).css("zIndex"), 10);
    if(index_current > index_highest) {
        index_highest = index_current;
    }
});</code>

<code class="javascript">// Assuming a class exists for the divs
$(".div-class").each(function() {
    // ...
});</code>