// combobox.component.html

<div class="multiselect">
    <div class="selectbox" (click)="showCheckboxes()">
        <select>
            <option>Выбрать что-то</option>
        </select>

        <div class="over-select"></div>
    </div>

    <div class="checkboxes" *ngIf="checkboxesShown">
        <ng-container *ngFor="let todo of todos; let index = index">
            <label [attr.for]="index">
                <input type="checkbox" [attr.id]="index" [checked]="todo.completed" (change)="checkTodo(todo)">
                {{ todo.title }}
            </label>
        </ng-container>
    </div>
</div>