Encode text method Thunder

EncodeText.user.js

// ==UserScript==
// @name         EncodeText
// @namespace    mangareader
// @version      0.23
// @description  Codificar texto, activar con Ctrl + Shift + H, desactivar con Esc
// @author       http://www.taringa.net/MangaReader/
// @match        http://*/*
// @match        https://*/*
// @grant        none
// ==/UserScript==
var v = ['a','e','i','o','u'];
var c = ['b','c','d','f','g','h','j','k','l','m','n','p','q','r','s','t','v','w','x','y','z'];

function isUpperCase(str) { 
	return (str == str.toUpperCase()); 
} 
function enc (str) {
	var newStr='', l, index, newIndex;
	for (var i = 0; i < str.length; i++) {
		var isUpp = isUpperCase(str[i]);
		l = str[i].toLowerCase();
		if(v.indexOf(l) != -1){//Es vocal
			index = v.indexOf(l);
			newIndex = (index != v.length - 1) ?  index+1 : 0;
			l = v[newIndex];
		}else if(c.indexOf(l) != -1){//Es consonante
			index = c.indexOf(l);
			newIndex = (index != c.length - 1) ?  index+1 : 0;
			l = c[newIndex];
		}
		if(isUpp) l = l.toUpperCase();
		newStr += l;
	}
	return newStr;
}
function dec (str) {
	var newStr='', l, index, newIndex;
	for (var i = 0; i < str.length; i++) {
		var isUpp = isUpperCase(str[i]);
		l = str[i].toLowerCase();
		if(v.indexOf(l) != -1){//Es vocal
			index = v.indexOf(l);
			newIndex = (index != 0) ?  index-1 :  v.length - 1;
			l = v[newIndex];
		}else if(c.indexOf(l) != -1){//Es consonante
			index = c.indexOf(l);
			newIndex = (index != 0) ?  index-1 :  c.length - 1;
			l = c[newIndex];
		}
		if(isUpp) l = l.toUpperCase();
		newStr += l;
	}
	return newStr;
}
function encDec (event) {
	var el = event.target;
	if(el.nodeName == 'TEXTAREA' || el.nodeName == 'INPUT'){
		el.value = enc(el.value);
	}else if (el.textContent != '') {
		var nodes = el.childNodes;
		for (var i = 0; i < nodes.length; i++) {
			if(nodes[i].nodeName == "#text"){
				nodes[i].nodeValue = dec(nodes[i].textContent);
			}
		}
	}
}
function highlight(event){
		var el = event.target;
		if ( el.nodeName == 'TEXTAREA' || el.nodeName == 'INPUT' || el.textContent != '') {
				event.target.style.cursor = 'pointer';
				event.target.style.textDecoration = 'underline';
		}
}
function restHigh(event){
		event.target.style.textDecoration = '';
		event.target.style.cursor = '';
}
function remListeners () {
	window.document.body.removeEventListener('mouseover',highlight);
	window.document.body.removeEventListener('mouseout',restHigh);
	window.document.body.removeEventListener('click',encDec);
}
function addListeners () {
	window.document.body.addEventListener('mouseover',highlight);
	window.document.body.addEventListener('mouseout',restHigh);
	window.document.body.addEventListener('click',encDec);
}
// Se activa con Ctrl+Shift+H
function onkeydown (event) {
	var k = event.keyCode;
	if (k == 27) {remListeners();} //Esc
	else if(event.shiftKey === true && event.ctrlKey === true && k == 72){
		addListeners();
	}
}
window.document.body.addEventListener('keydown', onkeydown);