logWrapper.js

var log = function(msg) {
  window.console &&
    typeof console.log === 'function' &&
    console.log(msg);
};

// http://tlrobinson.net/blog/2008/10/wrapping-javascript-callbacks/
function callbackWrap(object, property, argumentIndex, wrapperFactory, extra) {
    var original = object[property];
    object[property] = function() {
        arguments[argumentIndex] = wrapperFactory(arguments[argumentIndex], extra);
        return original.apply(this, arguments);
    };
    return original;
}

function logWrapper(func, msg) {
  return function() {
    log(msg);
    func.apply(this. arguments);
  };
}

callbackWrap(window, "setTimeout", 0, logWrapper, "wrapped a window.setTimeout!");
callbackWrap(window, "setInterval", 0, logWrapper, "wrapped a window.setInterval!");
callbackWrap(window, "addEventListener", 1, logWrapper, "wrapped a window.addEventListener!");
callbackWrap(Element.prototype, "addEventListener", 1, logWrapper, "wrapped a Element.addEventListener!");
callbackWrap(Document.prototype, "addEventListener", 1, logWrapper, "wrapped a Document.addEventListener!");