设置select元素中option的默认值

<select id="auth_access" class="form-control ">
  <option value="none">禁止</option>
  <option value="read">只读</option>
  <option value="write" selected>写入</option>
</select>

<select id="auth_access" class="form-control ">
  <option value="none">禁止</option>
  <option value="read">只读</option>
  <option value="write" selected="selected">写入</option>
</select>

document.getElementById('auth_access').selectedIndex = 1

$('#auth_access')[0].selectedIndex = 0