如何隐藏下拉菜单中未选中的项目？

Question

你好，我下拉菜单有问题。到目前为止，除了一件事之外，它的表现还不错。当选择一个选项时，它将转到顶部，仅显示其子项，而未显示所有其他类别。再次单击所选类别时，我们返回并查看其他类别。看看这个https://mmenujs.com/mhead/，我希望以相同的逻辑显示。我将在代码笔及以下提供代码。 Javascript对于解决问题最重要 Codepen：https://codepen.io/anon/pen/gVWrdm?editors=1010 应该如何：https://mmenujs.com/mhead/

HTML：

                        <div class="dropdown">
                            <button class="dropbtn dropbtn-three">
                                Parent
                                <i class="fa fa-caret-down"></i>
                            </button>
                            <div class="dropdown-content">
                                <ul>
                                    <li class="item-has-children">
                                        <a href="#0" class="padd-left">Child 1 <span class="rightt">  </span></a>
                                        <ul class="sub-menu">
                                            <li><a href="#0">Child 2 <span class="rightt">  </span></a>
                                                <ul class="sub-menu">
                                                        <li><a href="Drat.html">Child 3 </a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="litik.html">Child 3 </a></li> 
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropk.html">Child 3 Aussenpolitik </a></li> 
                                                </ul>
                                            </li>
                                        </ul>
                                    </li>

                                    <div class="hr2"></div>
                                    <li class="item-has-children">
                                        <a href="#0" class="padd-left">Child 1 <span class="rightt">  </span></a>
                                        <ul class="sub-menu">
                                            <li><a href="#">Liechtenstein und seine Nachbarn <span class="rightt">  </span></a>
                                                <ul class="sub-menu">
                                                        <li><a href="Droptml">Child 3 </a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropdows.html">Child 3</a></li>   
                                                </ul>
                                            </li>
                                            <div class="hr2"></div>
                                            <li><a href="#">Die Europapolitik <span class="rightt">  </span></a>
                                                <ul class="sub-menu">
                                                        <li><a href="Dro5.html">Child 3 </a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropdown3/.html">Child 3</a></li>  
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropdown3/a.html">Child 3 </a></li> 
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropdown3.html">Child 3 </a></li>  
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropd.html">Child 3 </a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropdown3.html">Child 3 </a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="Ds.html">Child 3 </a></li> 
                                                        <div class="hr2"></div>
                                                        <li><a href="D.html">Child 3</a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="O.html">Child 3</a></li> 
                                                </ul>
                                            </li> 
                                        </ul>
                                    </li>

                                    <div class="hr2"></div>
                                    <li class="item-has-children">
                                        <a href="#0" class="padd-left">Child 1<span class="rightt">  </span></a>
                                        <ul class="sub-menu">
                                            <li><a href="#">Die Vereinten Nationen <span class="rightt">  </span></a>
                                                <ul class="sub-menu">
                                                        <li><a href="Dropdown3/Lin.html">DChild 3</a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropdown3/i.html">Child 3</a></li> 
                                                        <div class="hr2"></div>
                                                        <li><a href="Dropn.html">Child 3</a></li>  
                                                        <li><a href="Drop.html">Child 3</a></li>   
                                                </ul>
                                            </li>
                                            <div class="hr2"></div>
                                            <li><a href="#">Child 3 <span class="rightt">  </span></a>
                                                <ul class="sub-menu">
                                                        <li><a href="Drop.html">Child 3</a></li>
                                                        <div class="hr2"></div>
                                                        <li><a href="Drom.html">Child 3 </a></li>   
                                                </ul>
                                            </li> 
                                        </ul>
                                    </li>
                                </ul>
                            </div>
                        </div>

CSS：

document.querySelectorAll(".item-has-children a").forEach(element => {
    element.addEventListener('click', () => {
        if (element.classList.contains('selected')) {
            const parentsibling = element.parentElement.parentElement.previousElementSibling;
            if (parentsibling) parentsibling.style.display = 'block';
            let nextSibling = element;
            while (nextSibling !== null && nextSibling.nodeName !== 'UL') {
                nextSibling = nextSibling.nextElementSibling;
            }
            if (nextSibling) nextSibling.style.display = 'none';
            element.classList.remove('selected');
        } else {
            const parentsibling = element.parentElement.parentElement.previousElementSibling;
            if (parentsibling) parentsibling.style.display = 'none';
            let nextSibling = element;
            while (nextSibling !== null && nextSibling.nodeName !== 'UL') {
                nextSibling = nextSibling.nextElementSibling;
            }
            if(nextSibling) nextSibling.style.display = 'block';
            element.classList.add('selected')
        }
    })
})

* {
    box-sizing: border-box;
}

body {
    display: flex;
    padding-top: 40px;
}

.dropdown {
    position: relative;
    display: inline-block;
    margin: 0 auto;
}

.dropdown .dropbtn {
    background-color: #153161;
    color: #ffffff;
    font-size: 17px;
    font-weight: 600;
    border: none;
    cursor: pointer;
    height: 55px;
    background: #153161;
    border-bottom-left-radius: 7px;
    border-bottom-right-radius: 7px;
    padding: 12px 50px;
    position: relative;
    width: 360px;
    text-align: left;
}

.dropdown .dropbtn i {
    margin-left: 30px;
    color: #8391ab;
    position: absolute;
    top: 50%;
    right: 25px;
    transform: translateY(-50%);
}

.dropdown .dropbtn .arrow {
    width: 0;
    height: 0;
    border-left: 10px solid transparent;
    border-right: 10px solid transparent;
    border-top: 10px solid #8191aa;
    margin: 100%;
    padding-top: 4px;
    z-index: 999;
}

.dropdown .dropbtn-two {
    background: #9a0000;
}

.dropdown .dropbtn-three {
    background: #000;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
    width: 330px;
    z-index: 999;
}

.dropdown-content a {
    color: black;
    padding: 12px 25px;
    text-decoration: none;
    display: flex;
    justify-content: flex-start;
    width: 100%;
}

.dropdown-content a:hover {
    background-color: #F8F8F8;
}

.dropdown-content a .rightt {
    display: inline-block;
    cursor: pointer;
    position: absolute;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    z-index: 999;
}

.dropdown-content a .rightt:after {
    content: '';
    display: inline-block;
    width: 9px;
    height: 9px;
    border-top: 0.2em solid #ababab;
    border-right: 0.2em solid #ababab;
    -moz-transform: rotate(45deg);
    -webkit-transform: rotate(45deg);
    transform: rotate(45deg);
}

.dropdown-content a.selected {
    padding-left: 70px;
}

.dropdown-content a.selected .rightt {
    left: 40px;
    top: 25%;
    right: auto;
    transform: translateY(0);
    transform: rotate(180deg);
}

.dropdown-content .left {
    display: inline-block;
    cursor: pointer;
    position: absolute;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    z-index: 999;
}

.dropdown-content .left:after {
    content: '';
    display: inline-block;
    width: 29px;
    height: 29px;
    border-top: 0.2em solid #ababab;
    border-right: 0.2em solid #ababab;
    -moz-transform: rotate(45deg);
    -webkit-transform: rotate(45deg);
    transform: rotate(45deg);
}

.dropdown-content .item-has-children a {
    position: relative;
}

.dropdown:hover .dropdown-content {
    display: block;
    background: white;
    opacity: 0.95;
    width: 100%;
}

.hr2 {
    height: 1px;
    background: #ccc;
    border-bottom: 1px solid #fff;
    border-top: 1px solid #ccc;
}

.sub-menu {
    display: none;
}

.sub-menu.selected {
    display: flex;
    flex-direction: column;
    transition: transform 0.6s;
}

ul {
    list-style: none;
    padding: 0 0px;
    width: 100%;
    height: 100%;
}

                            <div class="dropdown">
                                <button class="dropbtn dropbtn-three">
                                    Parent
                                    <i class="fa fa-caret-down"></i>
                                </button>
                                <div class="dropdown-content">
                                    <ul>
                                        <li class="item-has-children">
                                            <a href="#0" class="padd-left">Child 1 <span class="rightt">  </span></a>
                                            <ul class="sub-menu">
                                                <li><a href="#0">Child 2 <span class="rightt">  </span></a>
                                                    <ul class="sub-menu">
                                                            <li><a href="Drat.html">Child 3 </a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="litik.html">Child 3 </a></li> 
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropk.html">Child 3 Aussenpolitik </a></li> 
                                                    </ul>
                                                </li>
                                            </ul>
                                        </li>

                                        <div class="hr2"></div>
                                        <li class="item-has-children">
                                            <a href="#0" class="padd-left">Child 1 <span class="rightt">  </span></a>
                                            <ul class="sub-menu">
                                                <li><a href="#">Liechtenstein und seine Nachbarn <span class="rightt">  </span></a>
                                                    <ul class="sub-menu">
                                                            <li><a href="Droptml">Child 3 </a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropdows.html">Child 3</a></li>   
                                                    </ul>
                                                </li>
                                                <div class="hr2"></div>
                                                <li><a href="#">Die Europapolitik <span class="rightt">  </span></a>
                                                    <ul class="sub-menu">
                                                            <li><a href="Dro5.html">Child 3 </a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropdown3/.html">Child 3</a></li>  
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropdown3/a.html">Child 3 </a></li> 
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropdown3.html">Child 3 </a></li>  
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropd.html">Child 3 </a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropdown3.html">Child 3 </a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="Ds.html">Child 3 </a></li> 
                                                            <div class="hr2"></div>
                                                            <li><a href="D.html">Child 3</a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="O.html">Child 3</a></li> 
                                                    </ul>
                                                </li> 
                                            </ul>
                                        </li>

                                        <div class="hr2"></div>
                                        <li class="item-has-children">
                                            <a href="#0" class="padd-left">Child 1<span class="rightt">  </span></a>
                                            <ul class="sub-menu">
                                                <li><a href="#">Die Vereinten Nationen <span class="rightt">  </span></a>
                                                    <ul class="sub-menu">
                                                            <li><a href="Dropdown3/Lin.html">DChild 3</a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropdown3/i.html">Child 3</a></li> 
                                                            <div class="hr2"></div>
                                                            <li><a href="Dropn.html">Child 3</a></li>  
                                                            <li><a href="Drop.html">Child 3</a></li>   
                                                    </ul>
                                                </li>
                                                <div class="hr2"></div>
                                                <li><a href="#">Child 3 <span class="rightt">  </span></a>
                                                    <ul class="sub-menu">
                                                            <li><a href="Drop.html">Child 3</a></li>
                                                            <div class="hr2"></div>
                                                            <li><a href="Drom.html">Child 3 </a></li>   
                                                    </ul>
                                                </li> 
                                            </ul>
                                        </li>
                                    </ul>
                                </div>
                            </div>

Javascript：

document.querySelectorAll(".item-has-children a").forEach(element => {
    element.addEventListener('click', () => {
        if (element.classList.contains('selected')) {
            const parentsibling = element.parentElement.parentElement.previousElementSibling;
            if (parentsibling) parentsibling.style.display = 'block';
            let nextSibling = element;
            while (nextSibling !== null && nextSibling.nodeName !== 'UL') {
                nextSibling = nextSibling.nextElementSibling;
            }
            if (nextSibling) nextSibling.style.display = 'none';
            element.classList.remove('selected');
        } else {
            const parentsibling = element.parentElement.parentElement.previousElementSibling;
            if (parentsibling) parentsibling.style.display = 'none';
            let nextSibling = element;
            while (nextSibling !== null && nextSibling.nodeName !== 'UL') {
                nextSibling = nextSibling.nextElementSibling;
            }
            if(nextSibling) nextSibling.style.display = 'block';
            element.classList.add('selected')
        }
    })
})