CODE:

bot.addListener("message", function(from, to, text, message){
	function seen(input, func){
		if (text.indexOf("!!" + input) == 0){
			func(message.slice(input.length + 3))
		}
	}
	seen("insult", function(input){
		bot.say(to, "Fuck you, " + (input == "" ? from : input))
	});
	seen("add", function(input){
		if (isNaN(input)){
			number++;
		}
		else{
			number += input
		}
		bot.say(to, "It's " + number)
	});
});

ERROR:

maxell@MAXELL-PC E:\sd
> node app.js
E:\sd\node_modules\irc\lib\irc.js:748
                        throw err;
                              ^
TypeError: undefined is not a function
    at seen (E:\sd\app.js:10:17)
    at Client.<anonymous> (E:\sd\app.js:16:2)
    at Client.emit (events.js:118:17)
    at Client.<anonymous> (E:\sd\node_modules\irc\lib\irc.js:517:22)
    at Client.emit (events.js:107:17)
    at iterator (E:\sd\node_modules\irc\lib\irc.js:745:26)
    at Array.forEach (native)
    at Socket.<anonymous> (E:\sd\node_modules\irc\lib\irc.js:740:15)
    at Socket.emit (events.js:107:17)
    at readableAddChunk (_stream_readable.js:163:16)