Finally found solution.
MutationObserver = window.MutationObserver || window.WebKitMutationObserver;
var observer = new MutationObserver(function() {
$("a").attr("target", "_blank");
$("div").attr("title", Math.floor(Math.random() * 1000));
});
observer.observe(document, {
subtree: true,
childList: true
});
In options you need subtree: true
always, and if you changes attributes do not add to options attributes: true
because MutationObserver(function(mutations, observer) {
will go into the eternal cycle and browser freezes.