IIchan скрывалка тредов

// ==UserScript==
// @name         Hide thread iichan
// @namespace    http://iichan.hk/
// @license      WTFPL
// @version      0.1
// @description  adds hide thread feature to iichan
// @author       Cirno
// @match        http://iichan.hk/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    var THREAD_TITLE_LENGTH = 50;  // Сколько первых символов из поста показывать в заголовке скрытого треда

    function removeClass(element, className) {
        var reg = new RegExp('(\\s|^)' + className + '(\\s|$)');
        element.className = element.className.replace(reg, ' ');
    }

    function addHideBtns() {
        var threads = document.querySelectorAll('[id^=thread]');
        for (var i = threads.length - 1; i >= 0; i--) {
            var thread = threads[i];
            var label = thread.querySelector('label');
            if (!label) continue;
            var btn = document.createElement('a');
            btn.innerHTML = '[-]';
            btn.className = 'iichan-hide-thread-btn';
            btn.title = 'Скрыть тред';
            btn.addEventListener('click', function() {hideThread(thread.id);});
            thread.insertBefore(btn, label.nextSibling);
        }
    }

    function unHideThread(threadId) {
        var hiddenThreads = JSON.parse(window.localStorage.getItem('iichan_hidden_threads') || "[]");
        var index = hiddenThreads.indexOf(threadId);
        if (index === -1) {
            return;
        }
        hiddenThreads.splice(index, 1);
        window.localStorage.setItem('iichan_hidden_threads', JSON.stringify(hiddenThreads));

        var thread = document.getElementById(threadId);
        if(!thread) {
            return;
        }
        removeClass(thread, 'iichan-thread-hidden');
        var placeholder = document.getElementById('iichan-hidden-' + threadId);
        if (placeholder) {
            placeholder.parentElement.removeChild(placeholder);
        }
    }

    function hideThread(threadId) {
        var thread = document.getElementById(threadId);
        if(!thread) {
            return;
        }
        var parent = thread.parentNode;
        var threadHiddenDiv = document.createElement('div');
        var threadNo = threadId.split('-')[1];
        var threadTitle = thread.querySelector('.filetitle').innerText || thread.querySelector('blockquote').innerText || 'картинка';
        threadTitle = threadTitle.substr(0, THREAD_TITLE_LENGTH);
        threadHiddenDiv.innerHTML = 'Тред №' + threadNo + ' скрыт (' + threadTitle + ')';
        threadHiddenDiv.id = 'iichan-hidden-' + threadId;
        threadHiddenDiv.className = 'reply iichan-hidden-thread-placeholder';
        threadHiddenDiv.addEventListener('click', function() {unHideThread(threadId);});
        thread.className += ' iichan-thread-hidden';
        parent.insertBefore(threadHiddenDiv, thread);

        // save result
        var hiddenThreads = JSON.parse(window.localStorage.getItem('iichan_hidden_threads') || "[]");
        if (hiddenThreads.indexOf(threadId) === -1) {
            hiddenThreads.push(threadId);
            window.localStorage.setItem('iichan_hidden_threads', JSON.stringify(hiddenThreads));
        }
    }

    function hideAllHiddenThreads() {
        var hiddenThreads = JSON.parse(window.localStorage.getItem('iichan_hidden_threads') || "[]");
        for (var i = hiddenThreads.length - 1; i >= 0; i--) {
            hideThread(hiddenThreads[i]);
        }
    }

    function appendCSS() {
        var css = document.createElement('style');
        css.type = 'text/css';
        css.innerHTML =  '\
.iichan-hidden-thread-placeholder {\
cursor: pointer;\
}\
.iichan-hidden-thread-placeholder:hover + div, .iichan-hidden-thread-placeholder:hover + div + br {\
display: block !important;\
}\
.iichan-thread-hidden {\
display: none;\
}\
.iichan-thread-hidden + br {\
display: none;\
}\
.iichan-hide-thread-btn {\
margin-left: 0.2em;\
cursor: pointer;\
}\
';
        document.body.appendChild(css);
    }

    appendCSS();
    addHideBtns();
    hideAllHiddenThreads();
})();