我使用Bootstrap 4很好地创建了这个可折叠的导航栏，但是我希望当用户单击链接时将其关闭。有什么办法吗？谢谢

html导航栏：

<nav class="navbar navbar-toggleable-md fixed-top">

<button id="nav-btn"class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarDiv"  aria-expanded="false" aria-label="Toggle navigation">
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
 </button>

            <div class="container">

                <a class="navbar-brand" href="#"><img src="Images/logo.png" width="60px"></a>

                    <div class="collapse navbar-collapse" id="navbarDiv">

                        <ul class="navbar-nav mr-auto">

                            <li class="nav-item active">

                                <a class="nav-link" href="#home">Home <span class="sr-only">(current)</span></a>

                            </li>

                            <li class="nav-item">

                                <a class="nav-link" href="#about-us">About</a>

                            </li>

                            <li class="nav-item">

                                <a class="nav-link" href="#pricing">Pricing</a>

                            </li>

                        </ul>

                    </div>

            </div>

        </nav>

.icon-bar的css，因为Bootstrap 4不使用icon-bar类。

.navbar-toggler .icon-bar {
  margin: 7px;
  display: block;
  width: 22px;
  height: 1px;
  background-color: #cccccc;
  border-radius: 1px;
}