将所有子菜单放入列表中，然后添加单击侦听器，单击时，关闭列表中的所有子菜单，但单击的子菜单除外：

const subMenus = [];

document.querySelectorAll('.dropend .dropdown-toggle').forEach(function(menu, index) {
    
    subMenus.push(new bootstrap.Dropdown(menu));

    menu.addEventListener('click', function(e) {

        for (let i = 0; i < subMenus.length; i++) {
            if (i !== index) subMenus[i].hide();
        }

    });

});

工作片段：

document.addEventListener("DOMContentLoaded", function() {

    /////// Prevent closing from click inside dropdown
    document.querySelectorAll('.dropdown-menu').forEach(function(element) {
        element.addEventListener('click', function(e) {
            e.stopPropagation();
        });
    })

    const subMenus = [];

    document.querySelectorAll('.dropend .dropdown-toggle').forEach(function(menu, index) {
        
        subMenus.push(new bootstrap.Dropdown(menu));

        menu.addEventListener('click', function(e) {

            for (let i = 0; i < subMenus.length; i++) {
                if (i !== index) subMenus[i].hide();
            }

        });

    });


        // make it as accordion for smaller screens
        if (window.innerWidth < 992) {

            // close all inner dropdowns when parent is closed
            document.querySelectorAll('.navbar .dropdown').forEach(function(everydropdown){
                everydropdown.addEventListener('hidden.bs.dropdown', function () {
                    // after dropdown is hidden, then find all submenus
                      this.querySelectorAll('.submenu').forEach(function(everysubmenu){
                        // hide every submenu as well
                        everysubmenu.style.display = 'none';
                      });
                })
            });
            
            document.querySelectorAll('.dropdown-menu a').forEach(function(element){
                element.addEventListener('click', function (e) {
        
                    let nextEl = this.nextElementSibling;
                    if(nextEl && nextEl.classList.contains('submenu')) {    
                        // prevent opening link if link needs to open dropdown
                        e.preventDefault();
                        console.log(nextEl);
                        if(nextEl.style.display == 'block'){
                            nextEl.style.display = 'none';
                        } else {
                            nextEl.style.display = 'block';
                        }

                    }
                });
            })
        }
        // end if innerWidth
    
    
});

html {
    overflow-x: hidden;
}

body {
    padding-right: 0 !important;
    font-family: "Cera-PRO-Regular", Arial, sans-serif;
    font-weight: 300 !important;
    font-size: 1rem;
    line-height: 1.6;
    overflow-x: hidden;
    margin-top: 70px;
}

.navbar-collapse.in {
    max-height: 100%;
}

.no-border {
    border: none;
}

.menu-two li a.nav-link {
    color: white !important;
}

.navbar-collapse {
    padding-top: 70px;
    padding-left: 40px;
    padding-right: 40px;
}

.dropdown-menu li a {
    text-decoration: none;
    padding-left: 15px;
    font-weight: 400;
    color: #000;
}

.dropdown-menu {
    --bs-dropdown-padding-y: 0;
}

@media (min-width: 768px) {
    body {
        margin-top: 40px;
        /*130px;*/
    }
    .navbar-collapse {
        float: left;
        width: 100%;
        clear: both;
    }
    .navbar-inverse {
        border-top: 50px solid pink;
    }
    /*  .navbar-nav:nth-child(2) {
    margin-top: 20px; 
    clear: both;
  }
  .navbar-nav:nth-child(1) {
    margin-top: -20px; 
      clear: both;
  } */
}

.second-nav {
    margin-top: 40px;
}

li#search.nav-item {
    margin-left: 0;
}

.navbar {
    height: auto;
}

div.search-box.nav-link {
    margin-top: 30px;
}

nav ul,
.dropdown-menu li a {
    font-size: 0.875rem;
    font-weight: 700;
    padding: var(--bs-dropdown-item-padding-y) var(--bs-dropdown-item-padding-x);
    display: block;
}

.text-red {
    color: #D6001C;
}

.text-ltred {
    color: #FF435C;
}

.text-white {
    color: #fff;
}

.dropend .dropdown-menu[data-bs-popper] {
    background-color: lightgrey;
}

@media (min-width: 576px) {
    .navbar {
        height: auto;
    }
    li#search.nav-item {
        margin-left: 0;
    }
    div.search-box.nav-link {
        margin-top: 30px;
    }
    .navbar-expand-md .navbar-nav .nav-link {
        margin-right: 0.2rem;
        margin-left: 0.2rem;
        padding-right: 0;
        padding-left: 0;
    }
}

@media (min-width: 768px) {
    .navbar {
        height: 40px;
    }
    .navbar-brand img {
        left: 50px;
        top: 0;
        width: 160px;
    }
    .menu-one {
        margin-top: 50px;
    }
    .menu-two {
        margin-top: 10px;
    }
    .menu-two li a.nav-link {
        color: black !important;
    }
    .navbar-collapse {
        padding-top: 0px;
        padding-left: 0px;
        padding-right: 0px;
    }
    div.search-box.nav-link {
        margin-top: 0;
    }
    nav ul,
    .dropdown-menu li a {
        font-size: 0.75rem;
        font-weight: 700;
    }
    li#search.nav-item {
        margin-left: -1rem;
        /**was -3**/
    }
    .navbar-expand-md .navbar-nav .nav-link {
        margin-right: 0.6rem;
        margin-left: 0.6rem;
        padding-right: 0;
        padding-left: 0;
    }
    .dropend .dropdown-menu[data-bs-popper] {
        background-color: #fff;
    }
}

@media (min-width: 992px) {
    nav ul,
    .dropdown-menu li a {
        font-size: 1rem;
        font-weight: 700;
    }
    .navbar-expand-md .navbar-nav .nav-link {
        margin-right: 1rem;
        margin-left: 1rem;
        padding-right: 0;
        padding-left: 0;
    }
}

.navbar-nav {
    --bs-nav-link-padding-x: 0;
    --bs-nav-link-padding-y: 0.5rem;
    --bs-nav-link-font-weight: ;
    --bs-nav-link-color: #fff;
    --bs-nav-link-hover-color: #fff;
}

.btn-bd-primary {
    --bs-btn-color: #fff !important;
    --bs-btn-bg: #D6001C;
    --bs-btn-border-color: #D6001C;
    --bs-btn-hover-color: #D6001C !important;
    --bs-btn-hover-bg: #2E3138;
    --bs-btn-hover-border-color: #2E3138;
    --bs-btn-focus-shadow-rgb: 49, 132, 253;
    --bs-btn-active-color: #fff;
    --bs-btn-active-bg: #D6001C;
    --bs-btn-active-border-color: #D6001C;
    --bs-btn-active-shadow: inset 0 3px 5px rgba(0, 0, 0, 0.125);
    --bs-btn-disabled-color: #fff;
    --bs-btn-disabled-bg: #D6001C;
    --bs-btn-disabled-border-color: #D6001C;
    --bs-btn-border-radius: 1.5rem;
}

/**Start - Search box**/

/* div */

.search-box {
    position: relative;
    /*was absolute*/
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: #F6F6F6;
    /* was #cd595a;*/
    height: 30px;
    /*was 40px*/
    border-radius: 50px;
    padding: 0;
    /*was 10px*/
}

/* input */

.search-input {
    outline: none;
    border: none;
    background: none;
    width: 0;
    padding: 0;
    color: #2E3138;
    float: left;
    font-size: 14px;
    transition: .3s;
    line-height: 30px;
}

.search-input::placeholder {
    color: #dbc5b0;
}

/* icon */

.search-btn {
    color: #fff;
    float: right;
    width: 30px;
    height: 30px;
    border-radius: 50px;
    background: #222223;
    /* was #cd595a;*/
    display: flex;
    justify-content: center;
    align-items: center;
    text-decoration: none;
    transition: .3s;
}

.search-input:focus,
.search-input:not(:placeholder-shown) {
    width: 120px;
    /*was 240px*/
    padding: 0 6px;
}

.search-box:hover > .search-input {
    width: 120px;
    padding: 0 6px;
}

.search-box:hover > .search-btn,
.search-input:focus + .search-btn,
.search-input:not(:placeholder-shown) + .search-btn {
    background: #222223;
    color: #fff;
}

/**End - Search box**/

/**/

.dropdown-menu li {
    position: relative;
}

.dropdown-menu .dropdown-submenu {
    display: none;
    position: absolute;
    left: 100%;
    top: -7px;
}

.dropdown-menu .dropdown-submenu-left {
    right: 100%;
    left: auto;
}

.dropdown-menu > li:hover > .dropdown-submenu {
    display: block;
}

/**/

/*megamenu*/

.navbar .megamenu {
    padding: 1rem;
}

.navbar .megamenu {
    margin-top: 0px;
}

/* ============ desktop view ============ was 992px */

@media all and (min-width: 767px) {
    .navbar .has-megamenu {
        position: static !important;
    }
    .navbar .megamenu {
        left: 0;
        right: 0;
        width: 100%;
        margin-top: 70px;
    }
}

<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-MrcW6ZMFYlzcLA8Nl+NtUVF0sA7MsXsP1UyJoMp4YLEuNSfAP+JcXn/tWtIaxVXM" crossorigin="anonymous"></script>
<style>
html {
    overflow-x: hidden;
}

body {
    padding-right: 0 !important;
    font-family: "Cera-PRO-Regular", Arial, sans-serif;
    font-weight: 300 !important;
    font-size: 1rem;
    line-height: 1.6;
    overflow-x: hidden;
    margin-top: 70px;
}

.navbar-collapse.in {
    max-height: 100%;
}

.no-border {
    border: none;
}

.menu-two li a.nav-link {
    color: white !important;
}

.navbar-collapse {
    padding-top: 70px;
    padding-left: 40px;
    padding-right: 40px;
}

.dropdown-menu li a {
    text-decoration: none;
    padding-left: 15px;
    font-weight: 400;
    color: #000;
}

.dropdown-menu {
    --bs-dropdown-padding-y: 0;
}

@media (min-width: 768px) {
    body {
        margin-top: 40px;
        /*130px;*/
    }
    .navbar-collapse {
        float: left;
        width: 100%;
        clear: both;
    }
    .navbar-inverse {
        border-top: 50px solid pink;
    }
    /*  .navbar-nav:nth-child(2) {
    margin-top: 20px; 
    clear: both;
  }
  .navbar-nav:nth-child(1) {
    margin-top: -20px; 
      clear: both;
  } */
}

.second-nav {
    margin-top: 40px;
}

li#search.nav-item {
    margin-left: 0;
}

.navbar {
    height: auto;
}

div.search-box.nav-link {
    margin-top: 30px;
}

nav ul,
.dropdown-menu li a {
    font-size: 0.875rem;
    font-weight: 700;
    padding: var(--bs-dropdown-item-padding-y) var(--bs-dropdown-item-padding-x);
    display: block;
}

.text-red {
    color: #D6001C;
}

.text-ltred {
    color: #FF435C;
}

.text-white {
    color: #fff;
}

.dropend .dropdown-menu[data-bs-popper] {
    background-color: lightgrey;
}

@media (min-width: 576px) {
    .navbar {
        height: auto;
    }
    li#search.nav-item {
        margin-left: 0;
    }
    div.search-box.nav-link {
        margin-top: 30px;
    }
    .navbar-expand-md .navbar-nav .nav-link {
        margin-right: 0.2rem;
        margin-left: 0.2rem;
        padding-right: 0;
        padding-left: 0;
    }
}

@media (min-width: 768px) {
    .navbar {
        height: 40px;
    }
    .navbar-brand img {
        left: 50px;
        top: 0;
        width: 160px;
    }
    .menu-one {
        margin-top: 50px;
    }
    .menu-two {
        margin-top: 10px;
    }
    .menu-two li a.nav-link {
        color: black !important;
    }
    .navbar-collapse {
        padding-top: 0px;
        padding-left: 0px;
        padding-right: 0px;
    }
    div.search-box.nav-link {
        margin-top: 0;
    }
    nav ul,
    .dropdown-menu li a {
        font-size: 0.75rem;
        font-weight: 700;
    }
    li#search.nav-item {
        margin-left: -1rem;
        /**was -3**/
    }
    .navbar-expand-md .navbar-nav .nav-link {
        margin-right: 0.6rem;
        margin-left: 0.6rem;
        padding-right: 0;
        padding-left: 0;
    }
    .dropend .dropdown-menu[data-bs-popper] {
        background-color: #fff;
    }
}

@media (min-width: 992px) {
    nav ul,
    .dropdown-menu li a {
        font-size: 1rem;
        font-weight: 700;
    }
    .navbar-expand-md .navbar-nav .nav-link {
        margin-right: 1rem;
        margin-left: 1rem;
        padding-right: 0;
        padding-left: 0;
    }
}

.navbar-nav {
    --bs-nav-link-padding-x: 0;
    --bs-nav-link-padding-y: 0.5rem;
    --bs-nav-link-font-weight: ;
    --bs-nav-link-color: #fff;
    --bs-nav-link-hover-color: #fff;
}

.btn-bd-primary {
    --bs-btn-color: #fff !important;
    --bs-btn-bg: #D6001C;
    --bs-btn-border-color: #D6001C;
    --bs-btn-hover-color: #D6001C !important;
    --bs-btn-hover-bg: #2E3138;
    --bs-btn-hover-border-color: #2E3138;
    --bs-btn-focus-shadow-rgb: 49, 132, 253;
    --bs-btn-active-color: #fff;
    --bs-btn-active-bg: #D6001C;
    --bs-btn-active-border-color: #D6001C;
    --bs-btn-active-shadow: inset 0 3px 5px rgba(0, 0, 0, 0.125);
    --bs-btn-disabled-color: #fff;
    --bs-btn-disabled-bg: #D6001C;
    --bs-btn-disabled-border-color: #D6001C;
    --bs-btn-border-radius: 1.5rem;
}

/**Start - Search box**/

/* div */

.search-box {
    position: relative;
    /*was absolute*/
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: #F6F6F6;
    /* was #cd595a;*/
    height: 30px;
    /*was 40px*/
    border-radius: 50px;
    padding: 0;
    /*was 10px*/
}

/* input */

.search-input {
    outline: none;
    border: none;
    background: none;
    width: 0;
    padding: 0;
    color: #2E3138;
    float: left;
    font-size: 14px;
    transition: .3s;
    line-height: 30px;
}

.search-input::placeholder {
    color: #dbc5b0;
}

/* icon */

.search-btn {
    color: #fff;
    float: right;
    width: 30px;
    height: 30px;
    border-radius: 50px;
    background: #222223;
    /* was #cd595a;*/
    display: flex;
    justify-content: center;
    align-items: center;
    text-decoration: none;
    transition: .3s;
}

.search-input:focus,
.search-input:not(:placeholder-shown) {
    width: 120px;
    /*was 240px*/
    padding: 0 6px;
}

.search-box:hover > .search-input {
    width: 120px;
    padding: 0 6px;
}

.search-box:hover > .search-btn,
.search-input:focus + .search-btn,
.search-input:not(:placeholder-shown) + .search-btn {
    background: #222223;
    color: #fff;
}

/**End - Search box**/

/**/

.dropdown-menu li {
    position: relative;
}

.dropdown-menu .dropdown-submenu {
    display: none;
    position: absolute;
    left: 100%;
    top: -7px;
}

.dropdown-menu .dropdown-submenu-left {
    right: 100%;
    left: auto;
}

.dropdown-menu > li:hover > .dropdown-submenu {
    display: block;
}

/**/

/*megamenu*/

.navbar .megamenu {
    padding: 1rem;
}

.navbar .megamenu {
    margin-top: 0px;
}

/* ============ desktop view ============ was 992px */

@media all and (min-width: 767px) {
    .navbar .has-megamenu {
        position: static !important;
    }
    .navbar .megamenu {
        left: 0;
        right: 0;
        width: 100%;
        margin-top: 70px;
    }
}
</style>
<nav class="navbar navbar-expand-md navbar-dark fixed-top bg-dark">
    <div class="container-fluid"> <a class="navbar-brand" href="#"> LOGO </a>
        <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarCollapse" aria-controls="navbarCollapse" aria-expanded="false" aria-label="Toggle navigation"> <span class="navbar-toggler-icon"></span> </button>
        <!-- start test -->
        <div class="row navbar-collapse" id="navbarCollapse">
            <div class="col-md-12 order-last menu-one">
                <!-- start-->
                <ul class="navbar-nav ms-auto mb-2 mb-md-0 nav navbar-right justify-content-end">
                    <hr class="white d-block d-md-none">
                    <li class="nav-item"> <a class="nav-link active" aria-current="page" href="#">login </a> </li>
                    <li class="nav-item"> <a class="nav-link" href="#">support <span class="text-ltred">1300 000 123</span></a> </li>
                    <li class="nav-item dropdown"> <a class="nav-link dropdown-toggle" href="#" role="button" data-bs-toggle="dropdown" aria-expanded="false">  Global sites </a>
                        <ul class="dropdown-menu dropdown-menu-end">
                            <li><a class="dropdown-item" href="#">United States / Canada</a></li>
                            <li><a class="dropdown-item" href="#">New Zealand</a></li>
                        </ul>
                    </li>
                    <li class="nav-item" id="search">
                        <div class="search-box nav-link">
                            <input type="text" class="search-input" placeholder="Search">
                            <a class="search-btn" href="#"> ? </a> </div>
                    </li>
                </ul>
                <!-- end -->
            </div>
            <div class="col-md-12 order-md-last menu-two">
                <!-- start-->
                <ul class="navbar-nav ms-auto mb-2 mb-md-0 nav navbar-right justify-content-end">
                    <li class="nav-item dropdown has-megamenu"> <a class="nav-link dropdown-toggle" href="#" data-bs-toggle="dropdown">Solutions &amp; services</a>
                        <div class="dropdown-menu megamenu" role="menu">
                            <div class="row g-3">
                                <div class="col-md-6 col-12">
                                    <div class="col-megamenu">
                                        <h6 class="title">Solutions &amp; services</h6>
                                        <ul class="list-unstyled">
                                            <li class="dropend"> <a href="#" class="dropdown-item dropdown-toggle" data-bs-toggle="dropdown" aria-haspopup="true" data-bs-auto-close="true" aria-expanded="false">Leasing solutions</a>
                                                <ul class="dropdown-menu no-border">
                                                    <li><a class="dropdown-item" href=""> Transfer my fleet</a></li>
                                                    <li><a class="dropdown-item" href=""> Start a new fleet</a></li>
                                                    <li><a class="dropdown-item" href=""> Electric vehicles</a></li>
                                                    <li><a class="dropdown-item" href=""> Next lease</a></li>
                                                    <li><a class="dropdown-item" href=""> Trucks, plant &amp; equipment</a></li>
                                                    <li><a class="dropdown-item" href=""> Used vehicles</a></li>
                                                </ul>
                                            </li>
                                            <li class="dropend"> <a href="#" class="dropdown-item dropdown-toggle" data-bs-toggle="dropdown" aria-haspopup="true" data-bs-auto-close="true" aria-expanded="false">Fleet management services</a>
                                                <ul class="dropdown-menu no-border">
                                                    <li><a class="dropdown-item" href=""> Accident management</a></li>
                                                    <li><a class="dropdown-item" href=""> Acquisition and disposals</a></li>
                                                    <li><a class="dropdown-item" href=""> Driver safety</a></li>
                                                    <li><a class="dropdown-item" href=""> Fleet card</a></li>
                                                    <li><a class="dropdown-item" href=""> Hire vehicles</a></li>
                                                    <li><a class="dropdown-item" href=""> Infringement management</a></li>
                                                    <li><a class="dropdown-item" href=""> Insurance</a></li>
                                                    <li><a class="dropdown-item" href=""> Maintenance</a></li>
                                                    <li><a class="dropdown-item" href=""> PoolCar sharing platform</a></li>
                                                    <li><a class="dropdown-item" href=""> Registration</a></li>
                                                    <li><a class="dropdown-item" href=""> Roadside assistance</a></li>
                                                    <li><a class="dropdown-item" href=""> Telematics</a></li>
                                                    <li><a class="dropdown-item" href=""> Toll management</a></li>
                                                </ul>
                                            </li>
                                            <li class="dropend"> <a href="#" class="dropdown-item dropdown-toggle" data-bs-toggle="dropdown" aria-haspopup="true" data-bs-auto-close="true" aria-expanded="false">Fleet optimisation</a>
                                                <ul class="dropdown-menu no-border">
                                                    <li><a class="dropdown-item" href=""> Corporate financing</a></li>
                                                    <li><a class="dropdown-item" href=""> Leasing</a></li>
                                                    <li><a class="dropdown-item" href=""> Sales and lease back</a></li>
                                                    <li><a class="dropdown-item" href=""> Strategic consulting</a></li>
                                                    <li><a class="dropdown-item" href=""> Technology integration</a></li>
                                                </ul>
                                            </li>
                                        </ul>
                                    </div>
                                    <!-- col-megamenu.// -->
                                </div>
                                <!-- end col-3 -->
                            </div>
                            <!-- end row -->
                        </div>
                        <!-- dropdown-mega-menu.// -->
                    </li>
                    <li class="nav-item"> <a class="nav-link" href="#">Driver Support</a></li>
                    <li class="nav-item"> <a class="nav-link" href="#">About</a></li>
                    <li class="nav-item"> <a class="nav-link" href="#">News</a></li>
                    <li class="nav-item"> <a class="nav-link" href="#">Resources</a></li>
                    <li class="nav-item"> <a class="btn btn-bd-primary" href="#" role="button">Contact us</a></li>
                </ul>
                <!-- end -->
            </div>
        </div>
        <!-- end test -->
    </div>
</nav>

使用for循环遍历带有className=dropdown-menu的元素，并相应地更改它className
例如：

Array.from(document.querySelectorAll(".dropdown-menu")).forEach((e)=>{
       e.className=="hide"
       ?e.className=="show"
       :e.className=="hide"
   })