Angular 2 : In ngModelChange function how to compare old and new values of ngModel?

Question

I want to compare old and new values of ngmodel in ngModelchange function. I tried few solutions from stackoverflow but nothing is working in my case

This is my html code

<input type="text" [(ngModel)]="item.quantity" class="editInput" (ngModelChange)="rowchangcheck($event,item,i)" name="qty">

This is the function

 rowchangcheck(event, item, index) {
   console.log('oldvalue', item.quantity); //here value is getting changed
}

I have tried this but its not working stackoverflow answer

I want to get first value of ngModel before rowchange function and want to compare changed value with old one.How to do that please help

Have you looked at this [Angular 2 ngModelChange old value](https://stackoverflow.com/questions/41544086/angular-2-ngmodelchange-old-value) — Lasse, Dec 13 '17 at 08:53
@Lasse Did you read the question ? He puts a link to this question saying that it does not work for him. — ADreNaLiNe-DJ, Dec 13 '17 at 08:54
My bad - I had quit a few tabs open and took the wrong one.. — Lasse, Dec 13 '17 at 08:58
I have tried almost all the answers of stackoverflow but nothing is working in my case — Uidev123, Dec 13 '17 at 08:59

score 1 · Accepted Answer · answered Dec 13 '17 at 12:05

I tried a few things like you, and I could only get it to work for the second input - for my first input the old value would always be undefined

The best I can come up with as of now is to add an OldQuantity: plunker

rowchangcheck(oldValue, event, item) {
  console.log('oldValue', item.oldQuantity);
  console.log('newValue', event);
  item.oldQuantity = event;
}

1 Answers1