aria-label
正常情況下，form表單的input組件都有對應(yīng)的label.當(dāng)input組件獲取到焦點時，屏幕閱讀器會讀出相應(yīng)的label里的文本。
<!DOCTYPE html><html><head> <meta charset = "utf-8"> <title>demo</title> <link rel="stylesheet" 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">身份證號：</label> <div class="col-lg-7"> <input type = "text" id = "idCard" class="form-control"> </div> </div> </form></body></html>但是如果我們沒有給輸入框設(shè)置label時，當(dāng)其獲得焦點時，屏幕閱讀器會讀出aria-label屬性的值，aria-label不會在視覺上呈現(xiàn)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 = "身份證號"> </div> </div> </form></body>aria-labelledby<body> <div class="dropdown"> <button type="button" class="btn dropdown-toggle" id="dropdownMenu1" data-toggle="dropdown"> 選擇您的職位 <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" >測試工程師</a> </li> <li role="presentation"> <a role="menuitem" tabindex="-1" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" >開發(fā)工程師</a> </li> <li role="presentation"> <a role="menuitem" tabindex="-1" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" >銷售工程師</a> </li> </ul> </div></body>
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