要在不同屏幕尺寸的中心对齐项目，请使用justify-content-*-center类。
对于较小的屏幕尺寸，对齐后的弹性项目如下所示：
<div class="d-flex justify-content-sm-center bg-warning mb-5"> <div class="p-2 bg-danger">GOLF</div> <div class="p-2 bg-info">CRICKET</div> <div class="p-2 bg-secondary">SQUASH</div> </div>
对于中等尺寸的屏幕，对齐后的弹性项目如下所示：
<div class="d-flex justify-content-md-center bg-warning mb-5"> <div class="p-2 bg-danger">GOLF</div> <div class="p-2 bg-info">CRICKET</div> <div class="p-2 bg-secondary">SQUASH</div> </div>
对于大屏幕尺寸，对齐后的弹性项目如下所示：
<div class="d-flex justify-content-lg-center bg-warning mb-5"> <div class="p-2 bg-danger">GOLF</div> <div class="p-2 bg-info">CRICKET</div> <div class="p-2 bg-secondary">SQUASH</div> </div>
让我们看看如何实现justify-content-*-center-
<!DOCTYPE html> <html lang="en"> <head> <title>Bootstrap Example</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script> </head> <body> <div class="container mt-3"> <h3>Sports</h3> <h4>Centered on small screen</h4> <div class="d-flex justify-content-sm-center bg-warning mb-5"> <div class="p-2 bg-danger">GOLF</div> <div class="p-2 bg-info">CRICKET</div> <div class="p-2 bg-secondary">SQUASH</div> </div> <h4>Centered on medium screen</h4> <div class="d-flex justify-content-md-center bg-warning mb-5"> <div class="p-2 bg-danger">GOLF</div> <div class="p-2 bg-info">CRICKET</div> <div class="p-2 bg-secondary">SQUASH</div> </div> <h4>Centered on large screen</h4> <div class="d-flex justify-content-lg-center bg-warning mb-5"> <div class="p-2 bg-danger">GOLF</div> <div class="p-2 bg-info">CRICKET</div> <div class="p-2 bg-secondary">SQUASH</div> </div> </div> </body> </html>