How to group by some value in io-list?

Ionic Framework
1 
<ion-list *ngFor="let obj of data; let i=index">

  <ion-item-sliding>

      <ion-item>
        <div>UT_TXN_CODE: {{obj.UT_TXN_CODE}}</div>
        <br>Date {{obj.UT_LOG_DATE}}
        <br>Subject : {{obj.UT_SUBJECT}}
        <br>UT_LINK: {{obj.UT_LINK}}
      </ion-item>
      <ion-item-options side="right">
        <button ion-button color="secondary">
          <ion-icon name="checkmark"></ion-icon>
          Approve
        </button>
        <button ion-button color="blue">
          <ion-icon name="checkmark"></ion-icon>
          Send For<br> Approval
        </button>
      </ion-item-options>
    </ion-item-sliding>
  </ion-list>