jQuery clone duplicate IDs

I have an HTML element with a large collection of unordered lists contained within it. I need to clone this element to place elsewhere on the page with different styles added (this is simple enough using jQuery).

$("#MainConfig").clone(false).appendTo($("#smallConfig"));

The problem, however, is that all the lists and their associated list items have IDs and clone duplicates them. Is there an easy way to replace all these duplicate IDs using jQuery before appending?

If you need a way to reference the list items after you've cloned them, you must use classes, not IDs. Change all id="..." to class="..."

If you are dealing with legacy code or something and can't change the IDs to classes, you must remove the id attributes before appending.

$("#MainConfig").clone(false).find("*").removeAttr("id").appendTo($("#smallConfig"));

Just be aware that you don't have a way to reference individual items anymore.

Since the OP asked for a way to replace all the duplicate id's before appending them, maybe something like this would work. Assuming you wanted to clone MainConfig_1 in an HTML block such as this:

<div id="smallConfig">
    <div id="MainConfig_1">
        <ul>
            <li id="red_1">red</li>
            <li id="blue_1">blue</li>
        </ul>
    </div>
</div>

The code could be something like the following, to find all child elements (and descendants) of the cloned block, and modify their id's using a counter:

var cur_num = 1;    // Counter used previously.
//...
var cloned = $("#MainConfig_" + cur_num).clone(true, true).get(0);
++cur_num;
cloned.id = "MainConfig_" + cur_num;                  // Change the div itself.
$(cloned).find("*").each(function(index, element) {   // And all inner elements.
    if(element.id)
    {
        var matches = element.id.match(/(.+)_\d+/);
        if(matches && matches.length >= 2)            // Captures start at [1].
            element.id = matches[1] + "_" + cur_num;
    }
});
$(cloned).appendTo($("#smallConfig"));

To create new HTML like this:

<div id="smallConfig">
    <div id="MainConfig_1">
        <ul>
            <li id="red_1">red</li>
            <li id="blue_1">blue</li>
        </ul>
    </div>
    <div id="MainConfig_2">
        <ul>
            <li id="red_2">red</li>
            <li id="blue_2">blue</li>
        </ul>
    </div>
</div>

$("#MainConfig")
    .clone(false)
    .find("ul,li")
    .removeAttr("id")
    .appendTo($("#smallConfig"));

Try that on for size. :)

[Edit] Fixed for redsquare's comment.