HTML

angular input onchange

<input (change)="saverange()"/>

onchange event in angular

<input [value]="foo" (change)="changeFn($event)">
<input [ngModel]="bar" (ngModelChange)="modelChangeFn($event)">

angular onChange onChanges SimpleChanges

export class MyClassName implements OnInit,OnChanges {
 @Input() documents: Document[] = [];
.....
ngOnChanges(changes: SimpleChanges){
    console.log("changes ", changes)
    if(changes.documents){
      console.log("changes2 ", changes)
    }
  }