NG selectionStart

target.selectionStart 表示光标位置

<textarea [(ngModel)]="value" (keyup)="getCaretPosWithEvent($event)"></textarea>

getCaretPosWithEvent (event: { target: any; }) {
    const target = event.target;
    if (target.selectionStart || target.selectionStart === 0) {
      console.log(target.selectionStart);
    }
  }