<div class="container">
 <nav class="navbar navbar-default mynavbar">
 <div class="container-fluid">
  <!--按钮-->
  <div class="navbar-header">
  <button type="button" class="navbar-toggle collapsed btn-sider" data-toggle="collapse" data-target="#side-menu" aria-expanded="false">
   <span class="icon-bar"></span>
   <span class="icon-bar"></span>
   <span class="icon-bar"></span>
  </button>
  </div>

  <!-- 导航条内容 -->
  <div class="collapse navbar-collapse" id="side-menu">
  <ul class="nav navbar-nav" id="side-item">
   <li><a href="#">后端开发</a></li>
   <li><a href="#">数据库</a></li>
   <li class="dropdown">
   <a href="#" class="dropdown-toggle" id="web-item" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">前端开发 <span class="caret"></span></a>
   <!--下拉菜单按钮-->
   <ul class="dropdown-menu">
    <li><a href="#">HTML/CSS</a></li>
    <li><a href="#">JavaScript</a></li>
    <li><a href="#">jQuery</a></li>
    <li><a href="#">Bootstrap</a></li>
    <li><a href="#">node.js</a></li>
   </ul>
   </li>
   <li><a href="#">移动开发</a></li>
   <li><a href="#">视觉设计</a></li>
   <li><a href="#">云计算</a></li>
  </ul>
  </div>
 </div>
 </nav>
</div>

 .mynavbar{
  background-color: #fff;
  border:none;
 }
 .navbar-header,#side-item{
  background-color: #0b3558;
 }

 #side-menu>ul>li>a{
  color:#fff;
  font-size: 18px;
  font-family: "Microsoft Yahei", Helvetica, sans-serif, Lato;
 }
 #side-menu>ul{
  width: 100%;
 }
 #side-menu>ul>li{
  text-align: center;
  width: 16%;
  margin-left: 5px;
 }
 #side-menu .dropdown-menu {
  border: none;
  -webkit-box-shadow: 0 6px 12px rgba(0,0,0,.175);
  box-shadow: 0 6px 12px rgba(0,0,0,.175);
 }
 #side-item .dropdown-menu>li>a:focus, .dropdown-menu>li>a:hover,#side-item>li>a:focus,#side-item >li>a:hover {
  color: #24b0ff;
  text-decoration: none;
  background-color: transparent;
 }
 .btn-sider{
  float: left;
  border:none;
  outline: none;
  margin-left: 10px;
 }
 .mynavbar .btn-sider .icon-bar{
  background-color:#fff;
  width:23px;
  height:3px;
 }
 .mynavbar .btn-sider:focus, .mynavbar .btn-sider:hover {
  background-color: transparent;
 }
 @media (max-width: 768px) {
  .container {
  padding-left: 0px;
  }
  #side-menu{
  border: none;

  }
  #side-item{
  background: rgba(43, 54, 67, 0.97);
  }
  #side-menu>ul {
  margin-top: 0px;
  margin-right: 0px;
  margin-left: -15px;
  margin-bottom: 0px;
  width: 40%;
  height: 999px;
  }
  #side-menu>ul>li {
  text-align: left;
  width:100%;
  margin-left:0px;
  }
  #side-menu>ul>li a{
  font-size:16px;
  }
  #side-item>li>a:focus,#side-item >li>a:hover,#side-item .dropdown-menu>li>a:focus, .dropdown-menu>li>a:hover{
  background-color: #38a99c;
  color:#fff;
  }
  #side-menu .dropdown-menu{
  box-shadow:none;
  }
  #side-menu .dropdown-menu li a{
  padding-top:10px;
  color:#fff;
  }
 }