angularJS apply CSS after ng-if loads code example

Example: ngif

<div *ngIf="condition; else elseBlock">
         
<button class="xx" *ngIf="flag" (click)="doFunct()">Next</button>
   
--While (t/f boolean variable called "flag") is true
  This button will be visible + click button executes function
  Once this "flag" becomes false this button disapears