Bootstrap的aria-label和aria-labelledby属性实例详解

2018-11-02 7 Mr.zengcx

aria-label

正常情况下,form表单的input组件都有对应的label.当input组件获取到焦点时,屏幕阅读器会读出相应的label里的文本。

<!DOCTYPE html>
<html>
<head>
  <meta charset = "utf-8">
  <title>demo</title>
  <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="external nofollow" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
  <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
 <script src="https://cdn.bootcss.com/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
 <script src="https://cdn.bootcss.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
  <style type="text/css">
    body{padding: 20px;}
  </style>
</head>
<body>
  <form role = "form">
    <div class="form-group col-lg-3 form-horizontal">
      <label for = "idCard" class="control-label col-lg-5">身份证号:</label>
      <div class="col-lg-7">
        <input type = "text" id = "idCard" class="form-control">
      </div>    
    </div>  
  </form>
</body>
</html>

但是如果我们没有给输入框设置label时,当其获得焦点时,屏幕阅读器会读出aria-label属性的值,aria-label不会在视觉上呈现效果。

<body>
  <form role = "form">
    <div class="form-group col-lg-3 form-horizontal">
      <div class="col-lg-7">
        <input type = "text" id = "idCard" class="form-control" aria-label = "身份证号">
      </div>    
    </div>  
  </form>
</body>

aria-labelledby
<body>
  <div class="dropdown">
    <button type="button" class="btn dropdown-toggle" id="dropdownMenu1" 
     data-toggle="dropdown">
     选择您的职位
     <span class="caret"></span>
    </button>
    <ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
     <li role="presentation">
       <a role="menuitem" tabindex="-1" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" >测试工程师</a>
     </li>
     <li role="presentation">
       <a role="menuitem" tabindex="-1" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" >开发工程师</a>
     </li>
     <li role="presentation">
       <a role="menuitem" tabindex="-1" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" >销售工程师</a>
     </li>     
    </ul>
  </div>
</body>

注:

如果一个元素同时有aria-labelledby和aria-label,读屏软件会优先读出aria-labelledby的内容

总结

以上所述是小编给大家介绍的Bootstrap的aria-label和aria-labelledby属性实例详解,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对三水点靠木网站的支持!

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