CSS/JavaScript: Make element top-most z-index/top-most modal element

Question

I would like to make an element (e.g. a <div>) be the top-most layer on the page.

My assumption is that the only way I can do this is to specify that the element has a style="z-index:" value that is the maximum the browser allows (int32?).

Is this correct?

Instead, would it be possible to somehow get the element's z-index whose is highest, and make this <div>'s z-index the [highest element's value] + 1? For example:

$myDiv.css("z-index", $(document.body).highestZIndex() + 1);

How do modal JavaScript "windows" work?

Answer 1

Here's how to do it :

var elements = document.getElementsByTagName("*");
var highest_index = 0;

for (var i = 0; i < elements.length - 1; i++) {
    if (parseInt(elements[i].style.zIndex) > highest_index) {
        highest_index = parseInt(elements[i].style.zIndex;
    }
}

highest_index now contains the highest z-index on the page... just add 1 to that value and apply it wherever you want. You can apply it like so :

your_element.style.zIndex = highest_index + 1;

Here's another way of achieving the same thing using jQuery :

var highest_index = 0;

$("[z-index]").each(function() {
    if ($(this).attr("z-index") > highest_index) {
         highest_index = $(this).attr("z-index");
    }
});

Again, same way to apply the new index to an element :

$("your_element").attr("z-index", highest_index + 1);