在处理嵌套溢出时如何显示正确的滚动条？

Question

单击Services菜单项时，一切正常，但父级滚动条显示在子项滚动条的顶部。我仍然可以在子菜单中正确滚动，但是没有用可见滚动条模拟。

当我从overflow: auto;容器中删除.sidebar时，子菜单滚动工作正常，但父菜单没有。

如何确保可见滚动条适用于处于活动状态的菜单？

( function( $ ) {

	var sidebar = $( '.sidebar' );
  var menu = sidebar.find( '> ul, > div > ul' );

	// submenus
  ( function() {
  
  	if ( ! sidebar.length || ! menu.children().length || ! menu.length ) {
    	return;
    }
    
    var hasChildren = menu.find( '.has-children > a' );
    var goBack = menu.find( '.go-back' );
    var toggleSub = function( e ) {
    	e.preventDefault();
      var _this;
      
      if ( ! $( e.target ).closest( '.go-back' ).length ) {
      	_this = $( this );
      } else {
      	_this = $( this ).closest( '.sub-menu' ).prev();
      }
      
      _this.find( '~ .sub-menu' ).toggleClass( 'active' );
      _this.closest( 'ul' ).toggleClass( 'slide-out' );
    };
    
    hasChildren.on( 'click', toggleSub );
    goBack.on( 'click', toggleSub );
  
  } ) ();

} ) ( jQuery );

html, body {
  height: 100%;
  background: #f5f5f5;
  font-family: Arial, Helvetica, Helvetica Neue, sans-serif;
}

.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 280px;
  height: 100%;
  background: #fe6570;
  box-shadow: 2px 0px 4px 0px rgba(50,50,50,0.5);
  overflow: auto;
}

.sidebar ul li a {
  display: block;
  padding: 0 1rem;
  color: rgba(255, 255, 255, 0.8);
  line-height: 3.5rem;
  text-transform: capitalize;
  text-decoration: none;
  border-bottom: 1px solid rgba(230, 230, 230, 0.2);
  transition: transform 0.3s ease-in-out;
}

.sidebar ul .has-children > a {
  position: relative;
}

.sidebar ul .has-children > a:after,
.sidebar .go-back > a:before {
  content: '›';
  position: absolute;
  font-size: 1.5rem;
  right: 1rem;
}

.sidebar .go-back > a:before {
  content: '‹';
  position: relative;
  right: initial;
  left: 0;
  margin-right: 10px;
}

.sidebar .sub-menu {
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  height: 100%;
  width: 280px;
  background: #fe8065;
  transition: transform 0.3s ease-in-out;
  transform: translateX(-100%);
}

.sidebar ul {
  overflow-y: auto;
  list-style: none;
  padding: 0;
}

.sidebar .sub-menu.active {
  transform: translateX(0);
}

.sidebar .slide-out > li > a {
  transform: translateX(100%);
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="sidebar">
  <ul>
    <li><a href="#">Home</a></li>
    <li><a href="#">About Us</a></li>
    <li class="has-children">
      <a href="#">Services</a>
      <ul class="sub-menu">
        <li class="go-back"><a href="#">Services</a></li>
        <li><a href="#">Consultations</a></li>
        <li><a href="#">Design &amp; Planning</a></li>
        <li><a href="#">Service Item 1</a></li>
        <li><a href="#">Service Item 2</a></li>
        <li><a href="#">Service Item 3</a></li>
      </ul>
    </li>
    <li><a href="#">Photo Gallery</a></li>
    <li><a href="#">Resources</a></li>
    <li><a href="#">Find a Location</a></li>
    <li><a href="#">Contact Us</a></li>
  </ul>
</div>

Answer 1

简单，在打开“服务”子菜单时，将.sidebar元素从overflow: auto;更改为overflow: hidden，如下所示：

( function( $ ) {

	var sidebar = $( '.sidebar' );
  var menu = sidebar.find( '> ul, > div > ul' );

	// submenus
  ( function() {
  
  	if ( ! sidebar.length || ! menu.children().length || ! menu.length ) {
    	return;
    }
    
    var hasChildren = menu.find( '.has-children > a' );
    var goBack = menu.find( '.go-back' );
    var toggleSub = function( e ) {
    	e.preventDefault();
      var _this;
      
      if ( ! $( e.target ).closest( '.go-back' ).length ) {
      	_this = $( this );
      } else {
      	_this = $( this ).closest( '.sub-menu' ).prev();
      }
      
      _this.find( '~ .sub-menu' ).toggleClass( 'active' );
      _this.closest( '.sidebar' ).toggleClass( 'overflow-off' );
      _this.closest( 'ul' ).toggleClass( 'slide-out' );
    };
    
    hasChildren.on( 'click', toggleSub );
    goBack.on( 'click', toggleSub );
  
  } ) ();

} ) ( jQuery );

html, body {
  height: 100%;
  background: #f5f5f5;
  font-family: Arial, Helvetica, Helvetica Neue, sans-serif;
}

.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: 280px;
  height: 100%;
  background: #fe6570;
  box-shadow: 2px 0px 4px 0px rgba(50,50,50,0.5);
  overflow: auto;
}

.overflow-off {
  overflow: hidden;
}

.sidebar ul li a {
  display: block;
  padding: 0 1rem;
  color: rgba(255, 255, 255, 0.8);
  line-height: 3.5rem;
  text-transform: capitalize;
  text-decoration: none;
  border-bottom: 1px solid rgba(230, 230, 230, 0.2);
  transition: transform 0.3s ease-in-out;
}

.sidebar ul .has-children > a {
  position: relative;
}

.sidebar ul .has-children > a:after,
.sidebar .go-back > a:before {
  content: '›';
  position: absolute;
  font-size: 1.5rem;
  right: 1rem;
}

.sidebar .go-back > a:before {
  content: '‹';
  position: relative;
  right: initial;
  left: 0;
  margin-right: 10px;
}

.sidebar .sub-menu {
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  height: 100%;
  width: 280px;
  background: #fe8065;
  transition: transform 0.3s ease-in-out;
  transform: translateX(-100%);
}

.sidebar ul {
  overflow-y: auto;
}

.sidebar .sub-menu.active {
  transform: translateX(0);
}

.sidebar .slide-out > li > a {
  transform: translateX(100%);
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="sidebar">
  <ul>
    <li><a href="#">Home</a></li>
    <li><a href="#">About Us</a></li>
    <li class="has-children">
      <a href="#">Services</a>
      <ul class="sub-menu">
        <li class="go-back"><a href="#">Services</a></li>
        <li><a href="#">Consultations</a></li>
        <li><a href="#">Design &amp; Planning</a></li>
        <li><a href="#">Service Item 1</a></li>
        <li><a href="#">Service Item 2</a></li>
        <li><a href="#">Service Item 3</a></li>
        <li><a href="#">Service Item 4</a></li>
        <li><a href="#">Service Item 5</a></li>
      </ul>
    </li>
    <li><a href="#">Photo Gallery</a></li>
    <li><a href="#">Resources</a></li>
    <li><a href="#">Find a Location</a></li>
    <li><a href="#">Contact Us</a></li>
  </ul>
</div>

有几种方法可以实现这一点，在上面的示例中我添加了

_this.closest( '.sidebar' ).toggleClass( 'overflow-off' );

到toggleSub函数，overflow-off类为：

.overflow-off {
  overflow: hidden;
}