Sorting DOM elements doesn't work in IE 8

Question

I'm trying to sort an array of list elements in IE8 like this:

function comparator(params) {
    var keepSelectedOnTop = params.keepSelectedOnTop;

    return function (a, b) {    // a, b are DOM objects
        a = $(a);  // wrap with jQuery
        b = $(b);

        if (keepSelectedOnTop) {
            if (a.is(".selected") && !b.is(".selected")) {
                return -1;
            } else if (!a.is(".selected") && b.is(".selected")) {
                return 1;
            }
        }

        return a.text().localeCompare(b.text());
    }
}

// ...

var items = $("ul li").detach().toArray();

items.sort(comparator(params));

This works for small lists, but when I have many elements I get an undefined is null or not an object error. When I break on the exception with the debugger b is undefined after the assignment.

Did anyone encounter this before? It works fine in other browsers and it seems perfectly valid JS.

PS the jQuery version is 1.7.2

Answer 1

Why sort?

var items = $("ul li")
items = [].concat(items.filter(".selected").toArray()
                  ,items.filter(":not(.selected)").toArray())

Answer 2

After several trial & error attempts it seems that changing the assignments in the comparator solves the issue, but it doesn't make sense:

function comparator(params) {
    var keepSelectedOnTop = params.keepSelectedOnTop;

    return function (aDom, bDom) {
        var a = $(aDom), b = $(bDom);  // Use different vars for the wrappers

        if (keepSelectedOnTop) {
            if (a.is(".selected") && !b.is(".selected")) {
                return -1;
            } else if (!a.is(".selected") && b.is(".selected")) {
                return 1;
            }
        }

        return a.text().localeCompare(b.text());
    }
}

For some reason the above works, but the initial version where I reassigned different values to the parameters doesn't.