How to ungroup all groups in a document?

Why this script doesn't end? The idea is to ungroup all the groups in the doc. 

    var doc = app.activeDocument;
    var exit;

    while (true) {
        exit = true;

        app.executeMenuCommand("selectall");
        var sel = doc.selection;

        for (var i = 0; i < sel.length; i++) {
            var item = sel[i];
            if (item.typename === "GroupItem") {
                app.executeMenuCommand("ungroup");
                alert('ungrouped!');
                exit = false;
                break;
            }
        }

        while (doc.selection.length > 0) {
            app.executeMenuCommand('deselectall');
            app.redraw();
        }

        if (exit) break;
    }

    alert('exit while loop');