What is the purpose of the dropdown-toggle class in bootstrap dropdowns?

Question

Dropdown menus work great with the dropdown-toggle bootstrap class that applies to the <button> element, so why use it first?

Answer 1

The dropdown-toggle class adds an outline: 0; button outline: 0; on :focus to the button, so when you click on the button, it will not have the blue border of the "active" element.

Check the following two locks:

 <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> <div class="container"> <h2>Dropdowns</h2> <p>The .divider class is used to separate links inside the dropdown menu with a thin horizontal line:</p> <div class="dropdown"> <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">Tutorials - no border <span class="caret"></span></button> <ul class="dropdown-menu"> <li><a href="#">HTML</a></li> <li><a href="#">CSS</a></li> <li><a href="#">JavaScript</a></li> <li class="divider"></li> <li><a href="#">About Us</a></li> </ul> </div> </div> <div class="container"> <h2>Dropdowns</h2> <p>The .divider class is used to separate links inside the dropdown menu with a thin horizontal line:</p> <div class="dropdown"> <button class="btn btn-default" type="button" data-toggle="dropdown">Tutorials - with border <span class="caret"></span></button> <ul class="dropdown-menu"> <li><a href="#">HTML</a></li> <li><a href="#">CSS</a></li> <li><a href="#">JavaScript</a></li> <li class="divider"></li> <li><a href="#">About Us</a></li> </ul> </div> </div> 

Answer 2

It adds the following CSS properties, but they affect the display of the contents of the drop-down button:

Basically this is a button inner box-shadow when .open , as well as removing color , background-color , border-color and outline (with :focus ). Here is a comparison between the two:

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" /> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> <!-- Single button --> <div class="btn-group"> <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> With .dropdown-toggle <span class="caret"></span> </button> <ul class="dropdown-menu"> <li><a href="#">Action</a> </li> <li><a href="#">Another action</a> </li> <li><a href="#">Something else here</a> </li> <li role="separator" class="divider"></li> <li><a href="#">Separated link</a> </li> </ul> </div> <!-- Single button --> <div class="btn-group"> <button type="button" class="btn btn-default" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> Without .dropdown-toggle <span class="caret"></span> </button> <ul class="dropdown-menu"> <li><a href="#">Action</a> </li> <li><a href="#">Another action</a> </li> <li><a href="#">Something else here</a> </li> <li role="separator" class="divider"></li> <li><a href="#">Separated link</a> </li> </ul> </div> 

Difference tested in Chrome, Opera and Safari: