optgroup在选择列表的末尾添加一个空：

 <select>
  <option selected="" disabled="">Select a value</option>
  <option>Grumpy wizards make toxic brew for the evil Queen and Jack</option>
  <option>Quirky spud boys can jam after zapping five worthy Polysixes</option>
  <option>The wizard quickly jinxed the gnomes before they vaporized</option>
  <option>All questions asked by five watched experts amaze the judge</option>
  <optgroup label=""></optgroup>
 </select>

与上面的答案类似，但使用 JS 为文档中的每个选择添加一个空的 optgroup：

// iOS 7 hack: Add an optgroup to every select in order to avoid truncating the content
if (navigator.userAgent.match(/(iPad|iPhone|iPod touch);.*CPU.*OS 7_\d/i)) {
    var selects = document.querySelectorAll("select");
    for (var i = 0; i < selects.length; i++ ){
        selects[i].appendChild(document.createElement("optgroup"));
    }
}

希望这对遇到同样问题的人有用。