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JavaScript

// ==UserScript==
// @name Opennet Unfold Comments
// @namespace My Scripts
// @match *://*.opennet.ru/*
// @version 1
// @grant none
// ==/UserScript==

window.addEventListener('DOMContentLoaded', unfoldComments);

function unfoldComments() {
  const $btn = document.querySelector('#openlnk');
  const isUnfoldMode = getCookie('ajaxmode') === '1';
  // eslint-disable-next-line no-eval
  if (!isUnfoldMode) $btn.click();
}

function getCookie(name) {
  const matches = document.cookie.match(
    new RegExp(
      // eslint-disable-next-line no-useless-escape
      `(?:^|; )${name.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g, '\\$1')}=([^;]*)`,
    ),
  );
  return matches ? decodeURIComponent(matches[1]) : undefined;
}