Confluence fancybox enhance navigation

gistfile1.js

// ==UserScript==
// @name         Confluence fancybox enhance navigation
// @version      0.0.1
// @description  add navigation through image previews
// @author       Jonathan Gotti
// @match        http://*/*
// @match        https://*/*
// ==/UserScript==
// update match rules for your domain
(function(){
	var slice = function(a) { return [].slice.call(a); },
		style =  document.createElement('style'),
		images = slice(document.querySelectorAll('img.confluence-embedded-image')),
		left = document.querySelector('a#fancybox-left'),
		right = document.querySelector('a#fancybox-right'),
		srcPrefix = window.location.origin
	;

	//left.style.display = right.style.display = 'block';
	style.innerHTML = "#fancybox-left, #fancybox-right{ display:block !important;} img.current{ outline:solid red 1px;}";
	document.body.appendChild(style);

	images = images.map(function(elmt) {
		return [elmt, srcPrefix + elmt.dataset.imageSrc];
	});


	function resetCurrentClass() {
		images.forEach(function(item){  item[0].classList.remove('current'); });
	}

	function getPos() {
		var src = document.querySelector('img#fancybox-img').src,
			pos = -1
		;
		images.some(function(item, key){
			if (item[1] === src) {
				pos = key;
				return true;
			}
		});
		return pos;
	}

	function goTo(pos) {
		resetCurrentClass();
		images[pos][0].click();
		images[pos][0].classList.add('current');
	}

	function next(){
		var pos = getPos() + 1;
		(pos >= images.length) && (pos = 0);
		goTo(pos);
	}

	function prev(){
		var pos = getPos() - 1;
		(pos < 0) && (pos = images.length - 1);
		goTo(pos);
	}

	left.addEventListener('click', prev);
	right.addEventListener('click', next);
	document.body.addEventListener('keydown', function(evt){
		switch(evt.keyIdentifier) {
			case 'U+001B':
				resetCurrentClass(); break;
			case 'Left':
				prev(); break;
			case 'Right':
				next(); break;
		}
	});
})();