how do I override appendChild()?

Question

appendChild = function(message) {
    console.log("intercepted!");
}

using the code above does not seem to work.

Anyone knows?

Answer 1

What you might want to replace is Element.prototype.appendChild but it's probably a bad idea.

This example adds the text intercepted in the inserted element :

var f = Element.prototype.appendChild;
Element.prototype.appendChild = function(){f.apply(this, arguments);arguments[0].innerHTML="!Intercepted!"; };
document.body.appendChild(document.createElement("div"));

Demonstration