It is not possible to modify the js alert() box title, but you can use other plugins to do that like
Bootbox.js[
^]
Code:
bootbox.dialog({
message: "I am a custom dialog",
title: "Custom title",
buttons: {
main: {
label: "Close",
className: "btn-default",
callback: function() {
Example.show("Primary button");
}
}
}
});