Javascript CheckTor library

checktor.js

<script>

  /*
    Copyright 2015 - Hermes Center - GlobaLeaks project
    Author <giovanni.pellerano@evilaliv3.org>

    Javascript CheckTor library
  */

  function redirectIfOnTor(url, test_url) {
    // Test if the user is using Tor and in that case
    // redirects the user to provided url

    try {

      if (typeof(test_url) === 'undefined') {
        var test_url = 'https://antani.tor2web.org/checktor';
      }

      if (window.XMLHttpRequest) {
        var xmlhttp = new XMLHttpRequest();

        xmlhttp.onreadystatechange=function() {
          if (xmlhttp.readyState==4 && xmlhttp.status==200) {
            if (xmlhttp.getResponseHeader("x-check-tor")) {
              window.location.href = url;
            }
          }
        }

        xmlhttp.open("GET", test_url, true);
        xmlhttp.send();

      }
    } catch(err) {

    }
  }

</script>