How to make active class when it have sub category?

Hello guys im tryna to make active class when is clicked on subcategory

            <div class="collapse navbar-collapse">
                <ul class="nav navbar-nav">
                    <li class="{{ isActive('/') }}"><a href="{{ url('/') }}"><b class="fa fa-home"></b> @lang('messages.home')</a></li>
                    @foreach ($categories as $cat)
                        <li class="{{ $cat->children->count() > 0 ? 'dropdown' : ''}} {{ isActive('/category/'.$cat->slug) }}">
                            <a href="{{ url('/category/'.$cat->slug) }}" class="{{ $cat->children->count() > 0 ? 'dropdown-toggle' : ''  }}"
                               data-toggle="{{ $cat->children->count() > 0 ? 'dropdown' : ''  }}">
                                {{$cat->name}} {!! $cat->children->count() > 0 ? '<b class="fa fa-caret-down"></b>' : '' !!}
                            </a>
                            <ul class="dropdown-menu">
                            @foreach($subcategories as $sub)
                                @if($sub->parent_id == $cat->id)
                                        <li><a href="{{ url('category/'.$sub->slug) }}">{{ $sub->name }}</a></li>
                                @endif
                            @endforeach
                            </ul>
                         </li>
                    @endforeach
                </ul>
            </div>

How it will be done (isActive function is my custom helper that i make here it is)

<?php
if(!function_exists("isActive")) {
    /**
     * @param $url
     * @return string
     */
    function isActive($url) {
        return $_SERVER['REQUEST_URI'] == $url ? 'active' : '';
    }
}