test.js

$(function() {
    $("#btn_plus").click(function() {
        $(this).remove();
        var t = document.getElementById("fragment").cloneNode(true),
            labels = t.content.querySelectorAll("label");
        for (var i = 0; i < labels.length; i++ ) {
            labels[i].setAttribute("for", labels[i].getAttribute("for") + "-" + "2");
        }
        var clone = document.importNode(t.content, true);
        document.getElementById("outgoing").appendChild(clone);
    })
})