在处理背景颜色叠加时，border-bottom不起作用

Question

单击菜单并打开时，叠加背景效果对h2标记下的border-bottom不起作用。

我该如何解决这个问题？

我该如何解决？

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function openNav() {
    document.getElementById("mySidenav").style.width = "250px";
    document.getElementById("main").style.marginLeft = "250px";
    document.body.style.backgroundColor = "rgba(0,0,0,0.4)";
}

function closeNav() {
    document.getElementById("mySidenav").style.width = "0";
    document.getElementById("main").style.marginLeft= "0";
    document.body.style.backgroundColor = "white";
}

＆＃13;

h2 {
	border-bottom: 1px solid #eee;
}
.sidenav {
    height: 100%;
    width: 0;
    position: fixed;
    z-index: 1;
    top: 0;
    left: 0;
    background-color: #111;
    overflow-x: hidden;
    transition: 0.5s;
    padding-top: 60px;
}

.sidenav a {
    padding: 8px 8px 8px 32px;
    text-decoration: none;
    font-size: 25px;
    color: #818181;
    display: block;
    transition: 0.3s;
}

.sidenav a:hover {
    color: #f1f1f1;
}

.sidenav .closebtn {
    position: absolute;
    top: 0;
    right: 25px;
    font-size: 36px;
    margin-left: 50px;
}

#main {
    transition: margin-left .5s;
    padding: 16px;
}

@media screen and (max-height: 450px) {
  .sidenav {padding-top: 15px;}
  .sidenav a {font-size: 18px;}
}

＆＃13;

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
  <a href="#">About</a>
  <a href="#">Services</a>
  <a href="#">Clients</a>
  <a href="#">Contact</a>
</div>

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
  <a href="#">About</a>
  <a href="#">Services</a>
  <a href="#">Clients</a>
  <a href="#">Contact</a>
</div>
<div id="main">
  <h2>Sidenav Push Example</h2>
  <img src="https://i.stack.imgur.com/cpi0Y.jpg">
  <p>Click on the element below to open the side navigation menu, and push this content to the right. Notice that we add a black see-through background-color to body when the sidenav is opened.</p>
  <span style="font-size:30px;cursor:pointer" onclick="openNav()">&#9776; open</span>
</div>

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Answer 1

更改background-color的{​​{1}}并不重叠。它只是将背景绘制成另一种颜色。这就是document.body的{​​{1}}根本不受影响的原因。

要进行叠加，您必须创建一个用作叠加层的单独元素。

border-color

h2

function openNav() {
    document.getElementById("mySidenav").style.width = "250px";
    document.getElementById("main").style.marginLeft = "250px";
    //document.body.style.backgroundColor = "rgba(0,0,0,0.4)";
    
    /* ADD THIS */
    document.getElementById('overlay').style.display = 'block';
}

function closeNav() {
    document.getElementById("mySidenav").style.width = "0";
    document.getElementById("main").style.marginLeft= "0";
    //document.body.style.backgroundColor = "white";
    
    /* ADD THIS */
    document.getElementById('overlay').style.display = 'none';
}

您可以自行调整叠加层的h2 { border-bottom: 1px solid #eee; } .sidenav { height: 100%; width: 0; position: fixed; z-index: 1; top: 0; left: 0; background-color: #111; overflow-x: hidden; transition: 0.5s; padding-top: 60px; } .sidenav a { padding: 8px 8px 8px 32px; text-decoration: none; font-size: 25px; color: #818181; display: block; transition: 0.3s; } .sidenav a:hover { color: #f1f1f1; } .sidenav .closebtn { position: absolute; top: 0; right: 25px; font-size: 36px; margin-left: 50px; } #main { transition: margin-left .5s; padding: 16px; box-sizing: border-box; } /* ADD THIS */ #overlay { background-color: rgba(0, 0, 0, 0.4); position: absolute; top: 0; left: 0; display: none; height: 100%; width: 100%; } @media screen and (max-height: 450px) { .sidenav {padding-top: 15px;} .sidenav a {font-size: 18px;} }和<div id="mySidenav" class="sidenav"> <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a> <a href="#">About</a> <a href="#">Services</a> <a href="#">Clients</a> <a href="#">Contact</a> </div> <div id="main"> <!-- ADD THIS --> <div id="overlay"></div> <h2>Sidenav Push Example</h2> <img src="https://i.stack.imgur.com/cpi0Y.jpg"> <p>Click on the element below to open the side navigation menu, and push this content to the right. Notice that we add a black see-through background-color to body when the sidenav is opened.</p> <span style="font-size:30px;cursor:pointer" onclick="openNav()">&#9776; open</span> </div>。