Spy on jQuery event handlers to figure out what line of JS attached a called event

jquery-spy.js

(function() {
    var on = $.fn.on;
    $.fn.on = function() {
       var args=[], line = new Error().stack.split('\n')[1], fn=arguments[arguments.length-1];
       for (var i=0;i<arguments.length;i++) args[i] = arguments[i];
       args[args.length-1] = function() { console.log(line); return fn.apply(this, args); };
       on.apply(this, args);
       return this;
    };
})();