水平滚动时，子菜单不跟随主菜单

Question

一切正常，但是如果您将窗口缩小并水平滚动菜单，则子菜单与其父菜单不对齐：

https://jsfiddle.net/9hjgo1qc/7/

是否有任何关于如何使子菜单跟随滚动主菜单的想法？

HTML

<div class="navbar">
  <div class="dropdown">
    <button class="nav_button">M1</button>
  </div> 

  <div class="dropdown">
    <button class="nav_button">M2</button>
    <div class="dropdown-content">
      <button class="menu_sub_button">M2-1</button> 
      <button class="menu_sub_button">M2-2</button> 
    </div>
  </div>
  <div class="dropdown">
      <button class="nav_button">M3</button>
  </div> 
  <div class="dropdown">
    <button class="nav_button">M4</button>
  </div> 
</div> 
More text

CSS

.navbar {
    width:100%;
    overflow-x: auto;
    overflow-y: hidden;
    font-family: Arial, Helvetica, sans-serif;
    white-space: nowrap;
}
.navbar button {
    font-size: 12px;
    color: black;
    text-align: center;
    text-decoration: none;
}
.dropdown {
    overflow: auto;
    min-width: 180px;
    display: inline-block;
 }
.dropdown-content {
     display: none;
     position: absolute;
     background-color: #f9f9f9;
     min-width: 180px;
     box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
     z-index: 1;
}
.dropdown:hover .dropdown-content {
     display: block;
}
.nav_button {
     white-space: normal;
     width: 175px;
     height: 30px;
     display: block;
     text-align: left;
     color: black;
     border-style: none;
     background-color: #757BD3;
}
.menu_sub_button {
     white-space: normal;
     width: 175px;
     height: 25px;
     display: block;
     text-align: left;
     color: black;
     border-style: none;
     background-color: #D8D8D8;
}
.menu_sub_button:hover {
     background-color: #C3C3C3;
}

Answer 1

我已经改进了您的代码，它在台式机和智能手机上都能很好地运行

$("#cssmenu").menumaker({
    title: "Menu",
    breakpoint: 768,
    format: "multitoggle"
});

@import url(https://fonts.googleapis.com/css?family=Montserrat:400,700);
#cssmenu,
#cssmenu ul,
#cssmenu ul li,
#cssmenu ul li a,
#cssmenu #menu-button {
  margin: 0;
  padding: 0;
  border: 0;
  list-style: none;
  line-height: 1;
  display: block;
  position: relative;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
#cssmenu:after,
#cssmenu > ul:after {
  content: ".";
  display: block;
  clear: both;
  visibility: hidden;
  line-height: 0;
  height: 0;
}
#cssmenu #menu-button {
  display: none;
}
#cssmenu {
  font-family: Montserrat, sans-serif;
  background: #757bd3;
}
#cssmenu > ul > li {
  float: left;
}
#cssmenu.align-center > ul {
  font-size: 0;
  text-align: center;
}
#cssmenu.align-center > ul > li {
  display: inline-block;
  float: none;
}
#cssmenu.align-center ul ul {
  text-align: left;
}
#cssmenu.align-right > ul > li {
  float: right;
}
#cssmenu > ul > li > a {
  padding: 17px;
  font-size: 12px;
  letter-spacing: 1px;
  text-decoration: none;
  color: #dddddd;
  font-weight: 700;
  text-transform: uppercase;
}
#cssmenu > ul > li:hover > a {
  color: #ffffff;
}
#cssmenu > ul > li.has-sub > a {
  padding-right: 30px;
}
#cssmenu > ul > li.has-sub > a:after {
  position: absolute;
  top: 22px;
  right: 11px;
  width: 8px;
  height: 2px;
  display: block;
  background: #dddddd;
  content: '';
}
#cssmenu > ul > li.has-sub > a:before {
  position: absolute;
  top: 19px;
  right: 14px;
  display: block;
  width: 2px;
  height: 8px;
  background: #dddddd;
  content: '';
  -webkit-transition: all .25s ease;
  -moz-transition: all .25s ease;
  -ms-transition: all .25s ease;
  -o-transition: all .25s ease;
  transition: all .25s ease;
}
#cssmenu > ul > li.has-sub:hover > a:before {
  top: 23px;
  height: 0;
}
#cssmenu ul ul {
  position: absolute;
  left: -9999px;
}
#cssmenu.align-right ul ul {
  text-align: right;
}
#cssmenu ul ul li {
  height: 0;
  -webkit-transition: all .25s ease;
  -moz-transition: all .25s ease;
  -ms-transition: all .25s ease;
  -o-transition: all .25s ease;
  transition: all .25s ease;
}
#cssmenu li:hover > ul {
  left: auto;
}
#cssmenu.align-right li:hover > ul {
  left: auto;
  right: 0;
}
#cssmenu li:hover > ul > li {
  height: 35px;
}
#cssmenu ul ul ul {
  margin-left: 100%;
  top: 0;
}
#cssmenu.align-right ul ul ul {
  margin-left: 0;
  margin-right: 100%;
}
#cssmenu ul ul li a {
  border-bottom: 1px solid rgba(150, 150, 150, 0.15);
  padding: 11px 15px;
  width: 170px;
  font-size: 12px;
  text-decoration: none;
  color: #000000;
  font-weight: 400;
  background: #d8d8d8;
}
#cssmenu ul ul li:last-child > a,
#cssmenu ul ul li.last-item > a {
  border-bottom: 0;
}
#cssmenu ul ul li:hover > a,
#cssmenu ul ul li a:hover {
  color: #ffffff;
}
#cssmenu ul ul li.has-sub > a:after {
  position: absolute;
  top: 16px;
  right: 11px;
  width: 8px;
  height: 2px;
  display: block;
  background: #000000;
  content: '';
}
#cssmenu.align-right ul ul li.has-sub > a:after {
  right: auto;
  left: 11px;
}
#cssmenu ul ul li.has-sub > a:before {
  position: absolute;
  top: 13px;
  right: 14px;
  display: block;
  width: 2px;
  height: 8px;
  background: #000000;
  content: '';
  -webkit-transition: all .25s ease;
  -moz-transition: all .25s ease;
  -ms-transition: all .25s ease;
  -o-transition: all .25s ease;
  transition: all .25s ease;
}
#cssmenu.align-right ul ul li.has-sub > a:before {
  right: auto;
  left: 14px;
}
#cssmenu ul ul > li.has-sub:hover > a:before {
  top: 17px;
  height: 0;
}
#cssmenu.small-screen {
  width: 100%;
}
#cssmenu.small-screen ul {
  width: 100%;
  display: none;
}
#cssmenu.small-screen.align-center > ul {
  text-align: left;
}
#cssmenu.small-screen ul li {
  width: 100%;
  border-top: 1px solid rgba(120, 120, 120, 0.2);
}
#cssmenu.small-screen ul ul li,
#cssmenu.small-screen li:hover > ul > li {
  height: auto;
}
#cssmenu.small-screen ul li a,
#cssmenu.small-screen ul ul li a {
  width: 100%;
  border-bottom: 0;
}
#cssmenu.small-screen > ul > li {
  float: none;
}
#cssmenu.small-screen ul ul li a {
  padding-left: 25px;
}
#cssmenu.small-screen ul ul ul li a {
  padding-left: 35px;
}
#cssmenu.small-screen ul ul li a {
  color: #dddddd;
  background: none;
}
#cssmenu.small-screen ul ul li:hover > a,
#cssmenu.small-screen ul ul li.active > a {
  color: #ffffff;
}
#cssmenu.small-screen ul ul,
#cssmenu.small-screen ul ul ul,
#cssmenu.small-screen.align-right ul ul {
  position: relative;
  left: 0;
  width: 100%;
  margin: 0;
  text-align: left;
}
#cssmenu.small-screen > ul > li.has-sub > a:after,
#cssmenu.small-screen > ul > li.has-sub > a:before,
#cssmenu.small-screen ul ul > li.has-sub > a:after,
#cssmenu.small-screen ul ul > li.has-sub > a:before {
  display: none;
}
#cssmenu.small-screen #menu-button {
  display: block;
  padding: 17px;
  color: #dddddd;
  cursor: pointer;
  font-size: 12px;
  text-transform: uppercase;
  font-weight: 700;
}
#cssmenu.small-screen #menu-button:after {
  position: absolute;
  top: 22px;
  right: 17px;
  display: block;
  height: 4px;
  width: 20px;
  border-top: 2px solid #dddddd;
  border-bottom: 2px solid #dddddd;
  content: '';
  box-sizing: content-box;
}
#cssmenu.small-screen #menu-button:before {
  position: absolute;
  top: 16px;
  right: 17px;
  display: block;
  height: 2px;
  width: 20px;
  background: #dddddd;
  content: '';
  box-sizing: content-box;
}
#cssmenu.small-screen #menu-button.menu-opened:after {
  top: 23px;
  border: 0;
  height: 2px;
  width: 15px;
  background: #ffffff;
  -webkit-transform: rotate(45deg);
  -moz-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  -o-transform: rotate(45deg);
  transform: rotate(45deg);
}
#cssmenu.small-screen #menu-button.menu-opened:before {
  top: 23px;
  background: #ffffff;
  width: 15px;
  -webkit-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -ms-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
  transform: rotate(-45deg);
}
#cssmenu.small-screen .submenu-button {
  position: absolute;
  z-index: 99;
  right: 0;
  top: 0;
  display: block;
  border-left: 1px solid rgba(120, 120, 120, 0.2);
  height: 46px;
  width: 46px;
  cursor: pointer;
}
#cssmenu.small-screen .submenu-button.submenu-opened {
  background: #6269cd;
}
#cssmenu.small-screen ul ul .submenu-button {
  height: 34px;
  width: 34px;
}
#cssmenu.small-screen .submenu-button:after {
  position: absolute;
  top: 22px;
  right: 19px;
  width: 8px;
  height: 2px;
  display: block;
  background: #dddddd;
  content: '';
}
#cssmenu.small-screen ul ul .submenu-button:after {
  top: 15px;
  right: 13px;
}
#cssmenu.small-screen .submenu-button.submenu-opened:after {
  background: #ffffff;
}
#cssmenu.small-screen .submenu-button:before {
  position: absolute;
  top: 19px;
  right: 22px;
  display: block;
  width: 2px;
  height: 8px;
  background: #dddddd;
  content: '';
}
#cssmenu.small-screen ul ul .submenu-button:before {
  top: 12px;
  right: 16px;
}
#cssmenu.small-screen .submenu-button.submenu-opened:before {
  display: none;
}
#cssmenu.small-screen.select-list {
  padding: 5px;
}

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">

<!-- jQuery -->
<script src="http://code.jquery.com/jquery-latest.min.js"></script>

<!-- MenuMaker Plugin -->
<script src="https://s3.amazonaws.com/menumaker/menumaker.min.js"></script>

<!-- Icon Library -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">

<title>Test</title>
</head>

<body>
<div id="cssmenu">
  <ul>
     <li><a href="#" target="_blank"><i class="fa fa-fw fa-home"></i> Home</a></li>
     <li><a href="#"><i class="fa fa-fw fa-bars"></i> Menus</a>
        <ul>
           <li><a href="#">Sub menu 1</a>
              <ul>
                 <li><a href="#">Child menu 1</a></li>
                 <li><a href="#">Child menu 2</a></li>
              </ul>
           </li>
           <li><a href="#">Sub menu 2</a>
              <ul>
                 <li><a href="#">Child menu 1</a></li>
                 <li><a href="#">Child menu 2</a>
                    <ul>
                       <li><a href="#">Grand menu</a></li>
                    </ul>
                 </li>
              </ul>
           </li>
           <li><a href="#">Sub menu 3</a></li>
        </ul>
     </li>
     <li><a href="#"><i class="fa fa-fw fa-cog"></i> Settings</a></li>
     <li><a href="#"><i class="fa fa-fw fa-phone"></i> Contact</a></li>
  </ul>
</div>
</body>

</html>