<div id="accordian">
            <ul class="show-dropdown">
                <li>
                    <a href="javascript:void(0);"><i class="fas fa-tachometer-alt"></i>Dashboard</a>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-address-book"></i>Address Book</a>
                    <ul>
                        <li><a href="javascript:void(0);">Reports</a></li>
                        <li><a href="javascript:void(0);">Search</a></li>
                        <li><a href="javascript:void(0);">Graphs</a></li>
                        <li><a href="javascript:void(0);">Settings</a></li>
                    </ul>
                </li>
                <li class="active">
                    <a href="javascript:void(0);"><i class="far fa-clone"></i>Components</a>
                    <ul class="show-dropdown">
                        <li><a href="javascript:void(0);">Today's tasks</a></li>
                        <li class="active">
                            <a href="javascript:void(0);">DrillDown (active)</a>
                            <ul class="show-dropdown">
                                <li><a href="javascript:void(0);">Today's tasks</a></li>
                                <li class="active"><a href="javascript:void(0);">Urgent</a></li>
                                <li>
                                    <a href="javascript:void(0);">Overdues</a>
                                    <ul>
                                        <li><a href="javascript:void(0);">Today's tasks</a></li>
                                        <li><a href="javascript:void(0);">Urgent</a></li>
                                        <li><a href="javascript:void(0);">Overdues</a></li>
                                        <li><a href="javascript:void(0);">Recurring</a></li>
                                        <li>
                                            <a href="javascript:void(0);">Calendar</a>
                                            <ul>
                                                <li><a href="javascript:void(0);">Current Month</a></li>
                                                <li><a href="javascript:void(0);">Current Week</a></li>
                                                <li><a href="javascript:void(0);">Previous Month</a></li>
                                                <li><a href="javascript:void(0);">Previous Week</a></li>
                                                <li><a href="javascript:void(0);">Next Month</a></li>
                                                <li><a href="javascript:void(0);">Next Week</a></li>
                                                <li><a href="javascript:void(0);">Team Calendar</a></li>
                                                <li><a href="javascript:void(0);">Private Calendar</a></li>
                                                <li><a href="javascript:void(0);">Settings</a></li>
                                            </ul>
                                        </li>
                                    </ul>
                                </li>
                                <li><a href="javascript:void(0);">Recurring</a></li>
                                <li><a href="javascript:void(0);">Settings</a></li>
                            </ul>
                        </li>
                        <li>
                            <a href="javascript:void(0);">Overdues</a>
                            <ul>
                                <li><a href="javascript:void(0);">Today's tasks</a></li>
                                <li><a href="javascript:void(0);">Urgent</a></li>
                                <li><a href="javascript:void(0);">Overdues</a></li>
                                <li><a href="javascript:void(0);">Recurring</a></li>
                                <li><a href="javascript:void(0);">Settings</a></li>
                            </ul>
                        </li>
                        <li><a href="javascript:void(0);">Recurring</a></li>
                        <li><a href="javascript:void(0);">Settings</a></li>
                    </ul>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-calendar-alt"></i>Calendar</a>
                    <ul>
                        <li><a href="javascript:void(0);">Current Month</a></li>
                        <li><a href="javascript:void(0);">Current Week</a></li>
                        <li><a href="javascript:void(0);">Previous Month</a></li>
                        <li><a href="javascript:void(0);">Previous Week</a></li>
                        <li><a href="javascript:void(0);">Next Month</a></li>
                        <li><a href="javascript:void(0);">Next Week</a></li>
                        <li><a href="javascript:void(0);">Team Calendar</a></li>
                        <li><a href="javascript:void(0);">Private Calendar</a></li>
                        <li><a href="javascript:void(0);">Settings</a></li>
                    </ul>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-chart-bar"></i>Charts</a>
                    <ul>
                        <li><a href="javascript:void(0);">Global favs</a></li>
                        <li><a href="javascript:void(0);">My favs</a></li>
                        <li><a href="javascript:void(0);">Team favs</a></li>
                        <li><a href="javascript:void(0);">Settings</a></li>
                    </ul>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-copy"></i>Documents</a>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-bookmark"></i>Bookmarks</a>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-envelope"></i>Mail</a>
                </li>
                <li>
                    <a href="javascript:void(0);"><i class="far fa-heart"></i>Favorite</a>
                </li>

            </ul>
        </div>
* {
	margin: 0;
	padding: 0;
}
/* Scrollbar-effect------- */
#accordian::-webkit-scrollbar {
    width: 5px;
    height: 8px;
}
#accordian::-webkit-scrollbar-track {
    border-radius: 10px;
    background-color: #e4e4e4;
}
#accordian::-webkit-scrollbar-thumb {
    background: #0089ff;
    border-radius: 10px;
    transition: 0.5s;
}
#accordian::-webkit-scrollbar-thumb:hover {
    background: #d5b14c;
    transition: 0.5s;
}



/* --------- */
body {
	background: #4EB889;
	font-family: Nunito, arial, verdana;
}

#accordian {
	background: #fff;
	width: 250px;
	padding: 10px;
	float: left;
	height: 100vh;
	overflow-x: hidden;
}


#accordian a {
	
	
	
}


i {
	margin-right: 10px;
}

#accordian li {
	list-style-type: none;
}

#accordian ul li a{
	color: #9c9c9c;
	text-decoration: none;
	font-size: 15px;
	display: block;
/* 	line-height: 34px; */
	padding: 12px 15px;
	transition: all 0.15s;
	position: relative;
	border-radius: 3px;
}

#accordian>ul.show-dropdown>li.active>a,
#accordian>ul>li>ul.show-dropdown>li.active>a,
#accordian>ul>li>ul>li>ul.show-dropdown>li.active>a,
#accordian>ul>li>ul>li>ul>li>ul.show-dropdown>li.active>a,
#accordian>ul>li>ul>li>ul>li>ul>li>ul.show-dropdown>li.active>a{
	background-color: #a8d4fb;
    color: #0089ff;
    box-shadow: 0px 1px 2px rgba(0, 137, 255, 0.2);
}

#accordian>ul>li>ul,
#accordian>ul>li>ul>li>ul,
#accordian>ul>li>ul>li>ul>li>ul,
#accordian>ul>li>ul>li>ul>li>ul>li>ul {
	display: none;
}


#accordian>ul>li.active>ul.show-dropdown,
#accordian>ul>li>ul>li.active>ul.show-dropdown,
#accordian>ul>li>ul>li>ul>li.active>ul.show-dropdown,
#accordian>ul>li>ul>li>ul>li>ul>li.active>ul.show-dropdown {
	display: block;
}

#accordian>ul>li>ul,
#accordian>ul>li>ul>li>ul,
#accordian>ul>li>ul>li>ul>li>ul,
#accordian>ul>li>ul>li>ul>li>ul>li>ul {
	padding-left: 20px;
}

#accordian a:not(:only-child):after {
	content: "\f105";
    position: absolute;
    right: 20px;
    top: 14px;
    font-size: 15px;
    font-family: "Font Awesome 5 Free";
    display: inline-block;
    padding-right: 3px;
    vertical-align: middle;
    font-weight: 900;
    transition: 0.5s;
}

#accordian .active>a:not(:only-child):after {
		transform: rotate(90deg);
}
// -------multilevel-accordian-menu---------
$(document).ready(function() {
    $("#accordian a").click(function() {
        var link = $(this);
        var closest_ul = link.closest("ul");
        var parallel_active_links = closest_ul.find(".active")
        var closest_li = link.closest("li");
        var link_status = closest_li.hasClass("active");
        var count = 0;

        closest_ul.find("ul").slideUp(function() {
            if (++count == closest_ul.find("ul").length){
                parallel_active_links.removeClass("active");
                parallel_active_links.children("ul").removeClass("show-dropdown");
            }
        });

        if (!link_status) {
            closest_li.children("ul").slideDown().addClass("show-dropdown");
            closest_li.parent().parent("li.active").find('ul').find("li.active").removeClass("active");
            link.parent().addClass("active");
        }
    })
});






// --------for-active-class-on-other-page-----------
jQuery(document).ready(function($){
  	// Get current path and find target link
  	var path = window.location.pathname.split("/").pop();
  
  	// Account for home page with empty path
  	if ( path == '' ) {
    	path = 'index.html';
  	}
     
  	var target = $('#accordian li a[href="'+path+'"]');
  	// Add active class to target link
  	target.parents("li").addClass('active');
  	target.parents("ul").addClass("show-dropdown");
});

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.10.2/css/all.css

External JavaScript

  1. https://code.jquery.com/jquery-3.4.1.min.js