encode/decode email address in HTML

email.js

  var elements = document.querySelectorAll('[data-mailto]');
  for (var i = elements.length - 1; i >= 0; i--) {
    var el = elements[i];
    var email = '';
    for (var j = el.children.length - 1; j >= 0; j--) {
      if (el.children[j].style.display !== 'none') {
        email = el.children[j].innerText + email;
      }
    }
    el.innerHTML = email;
    el.href = 'mailto:' + email;
  }

email.php

function email($email)
{
  $res = '';
  $len = strlen($email);
  for ($i=0; $i < $len; $i++) { 
    $res .= sprintf('<span style="display: none;">%s</span><span>%s</span>', chr(rand(97, 122)), $email[$i]);
  }
  return $res;
}

PHP 5.2 and IE 10 tested.