如下图所示的外边界半径..?

Outward border radius like given in below picture..?

我正在使用 ant-d 导航栏,我必须制作一个如图所示的外边框。我怎样才能做到这一点?

您可以为每个菜单项指定顶部和底部 div 以配合每个菜单项,然后为其设置样式以提供您的边框半径。看看我为你做的这个例子:

var header = document.getElementById("cont");
var btns = header.getElementsByClassName("containerblue");
for (var i = 0; i < btns.length; i++) {
  btns[i].addEventListener("click", function() {
  var current = document.getElementsByClassName("active");
  current[0].className = current[0].className.replace(" active", "");
  this.className += " active";
  });
}
.container{
  background-color: skyblue;
  width: 300px;
}

.containerblue{
  background-color: blue;
  width: 20px;
  padding-left: 25px;
}


.containerblue.active > .top {
  background-color: blue;
  width: 200px;
  height: 25px;
  border-radius: 0px 0px 25px 0px;
  pointer-events: none;
}

.containerblue.active > .middle{
  background-color: skyblue;
  width: 200px;
  border-radius: 25px;
  padding: 20px;
}

.containerblue.active > .bottom {
  background-color: blue;
  width: 200px;
  height: 25px;
  border-radius: 0px 25px 0px 0px;
  pointer-events: none;
}


.top{
  background-color: blue;
  width: 200px;
  height: 25px;
  pointer-events: none;
}

.middle{
  background-color: blue;
  width: 200px;
  padding-top: 20px;
  padding-bottom: 20px;
  cursor: pointer;
  color: white;
}

.bottom{
  background-color: blue;
  width: 200px;
  height: 25px;
  pointer-events: none;
}
<div class="container" id="cont">
   <div class="containerblue active">
    <div class="btn top"></div>
    <div class="btn middle">Search</div>
    <div class="btn bottom"></div>
  </div>
   <div class="containerblue">
    <div class="btn top"></div>
    <div class="btn middle">Contracts</div>
    <div class="btn bottom"></div>
  </div>
   <div class="containerblue">
    <div class="btn top"></div>
    <div class="btn middle">Etc.</div>
    <div class="btn bottom"></div>
  </div>
</div>