warn when you're about to tweet "thanks to me"

thankstome.user.js

// ==UserScript==
// @name       Warn when you're about to tweet "thanks to me"
// @namespace  http://localhost/
// @version    0.1
// @description Add an alert whenever someone types "thanks to me"
// @match      http://twitter.com/*
// @match      https://twitter.com/*
// ==/UserScript==

(function() {
    var containing = false
    window.addEventListener("keyup", function(event) {
        function istweetbox_p(elem) {
            return elem.className.split(' ').indexOf('tweet-box') != -1 }
        function contains_selfishness_p(elem) {
            return !!elem.value.match(/thanks *to *me/i) }
        if (istweetbox_p(event.target)) {
            var tweetbox = event.target
            if (contains_selfishness_p(tweetbox)) {
                if (!containing) {
                    window.alert("You are about to tweet something containing"+
                    " \"thanks to me\", this was probably(hopefully) an error")
                    containing = true }}
            else if (containing)
                containing = false }}, false);

})();