<script>var get = location.hash.split('=')[1];var get = get.split ('&')[0]; // получаем access_token
  if(get) {

function callbackFunc(result) {
console.log(result.error.error_msg);
}



var url = "https://api.vk.com/method/groups.join?group_id=112450248&v=5.44&access_token=" + get;
  var script = document.createElement('SCRIPT');

script.src = url + "&callback=callbackFunc";

document.getElementsByTagName("head")[0].appendChild(script);

  };</script>`