static headerView() {
    const header = document.createElement('header');
    header.innerHTML = `
      <header>
          <h1 class = "site-name"> glebogram </h1>
          ${this.isLoggedUser ? `<button class="add-post"><i class="fas fa-plus fa-2x"></i></button>
          <div class = "user-name">gleb9990</div>
          <button id = "log-out"><img src="images/user-image.png" alt="user-image" id = "user-pic"></button>` : ''}
          <button id = "sign-in"><span>sign in</span></button>
      </header>`;
    const body = document.getElementsByTagName('body')[0];
    body.insertAdjacentElement('afterbegin', header);
  }