html javascript - Cancel focus on page for dropdown menu focus - html

Question

I need to make that the focus of the browser stays in a element even though the user keeps scrolling. Basically I have a dropdown menu with a scrollable feature so I need to keep the focus on it if the user leaves the pointer inside the menu and keeps scrolling.
It's than even possible? I'm new to html.
My html is (with some angular):
<ul ng-if="filter.isSearchListType && hasFilterValues(filter)" class="dropdown-menu scrollable-menu">
<li class="individual-search">
<input type="search" ng-model="searchInputText" class="form-group filter-input" placeholder="Nombre o E-mail" />
<i ng-show="searchInputText" class="fa fa-remove clear-search-icon" aria-hidden="true" ng-click="searchInputText = ''; $event.stopPropagation()"></i>
<i class="fa fa-search search-icon" aria-hidden="true" ng-click="$event.stopPropagation()"></i>
</li>
<li ng-repeat="filterValue in filter.values | searchInData:searchInputText">
<a href="#" ng-click="selectFilterValue(filter, filterValue.id)" ng-class="{ 'selected': isSelectedFilter(filter, filterValue.id) }">
{{filterValue.label}}
</a>
</li>
</ul>
My css is:
.scrollable-menu {
height: auto;
max-height: 200px;
overflow-x: hidden;
}
And the render of this is:
DropDown-Menu Scrollable
And last, but it's not so important, it's posible to keep a li pin or fixed and make the rest of the li scrollable??
Thanks!!