导航条在Bootstrap的小屏幕上一秒钟后消失

Question

我使用bootstrap来实现一个切换导航条。在较小的屏幕上，它可以切换，但当我点击图标时，导航条会在一秒钟后出现并消失。有人能帮忙吗?我将在下面分享导航条形码。正如您所看到的，我已经添加了必要的类，但是导航条仍然会在一秒钟后消失在较小的屏幕上。我是新手。请帮帮我

<nav class="navbar  navbar-expand-sm  fixed-top navbar-default">  
<div class="navbar-header ">
<span  class="navbar-brand"> <img class="rounded d-inline-block align-top  "src="./mr.jpg" height="30px" width="30px" >HARISH</a></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</div>
<div class="container">
<button class="navbar-toggler  collapsed navbar-light " type="button" data-toggle="collapse" data-target = "#navbar" aria-controls = "navbarNav" aria-expanded = "false" aria-label = "Toggle navigation "> 
<span class="navbar-toggler-icon"></span>
</button>

<div class="collapse navbar-collapse navbar-toggleable" id="navbar">
<ul class=" nav navbar-nav ">
<a class="nav-item nav-link a-style" href="#">Reviews</a>
<a class="nav-item nav-link a-style" href="#">About us</a>
<a class="nav-item nav-link a-style" href="#">FAQ</a>
</ul>
</div>
</div> 
</nav>

Answer 1

Try This…

<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>

<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Link</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link disabled" href="#">Disabled</a>
</li>
</ul>
<form class="form-inline my-2 my-lg-0">
<input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
<button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
</form>
</div>
</nav>