window object does not provide any event like before-open (or other open-related events), so you can not intercept it...
The only known - to me - solution is to override window.open function...
window.open_original = window.open;
window.open = function(url, name, features, replace) {
alert("!");
window.open_original(url, name, features, replace);
}
window.open("http://www.codeproject.com");
http://jsfiddle.net/5fLkb2zx/[
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