src/app/lists/sorting/sorting.component.html

<ng-content>
</ng-content>
<i  class="fa" [ngClass]="{'fa-sort': initColumnName != columnName || defaultState, 
                          'fa-sort-asc': (initColumnName == columnName && !isDesc && !defaultState), 
                          'fa-sort-desc': (initColumnName == columnName && isDesc && !defaultState) }" aria-hidden="true"> 
        </i>