Angular 2/4 - How to access specific array in ngFor

Question

I've got an array of items in which I'm comparing a user id of the current element vs the previous one. When I try this code, it results in a blank page with no errors:

<ion-item *ngFor="let message of messages; let i = index;">
   <div *ngIf="message.user_id !== messages[i-1].user_id"></div>
</ion-item>

Can you not access array indexes in the template this way?

This example will probably fail for index [0] because [i-1] will be [-1] which doesn't exist — 0mpurdy
– 0mpurdy, Commented Aug 1, 2017 at 18:47

Reactgular · Accepted Answer · 2017-08-01 18:57:57Z

3

0-1 === -1 so skip the first item.

<ion-item *ngFor="let message of messages; let i = index; let isFirst = first">
   <div *ngIf="!isFirst && message.user_id !== messages[i-1].user_id"></div>
</ion-item>

answered Aug 1, 2017 at 18:57

Reactgular

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