How can I target the initial last element within an *ngFor loop?

In my current project using Ionic, I am developing a personal application where I aim to implement an alphabetical header/divider for a list of games. The idea is to check the first letter of each game, and whenever it differs from the last game's initial letter (assuming they are sorted), a header should be generated.

Let me share my `firstLetter()` function with you:

public firstLetter(name: any) {
    return name.charAt(0);
}

Furthermore, here is the snippet from my HTML/ng file:

<ion-item-group *ngFor="let game of games; let i = index;">
        <ion-item-divider color="light" *ngIf="firstLetter(game.name) != firstLetter(game[i-1].name)">{{firstLetter(game.name)}}</ion-item-divider>
        <ion-item (click)="openGameSummary(game)">
          <h2>{{game.name}}</h2>
        </ion-item>
      </ion-item-group>

I am encountering an

error stating that the property 'name' cannot be found,
likely due to incorrect syntax usage on my end.

Can someone guide me on how to resolve this issue effectively?

Answer №1

Revise your *ngIf condition to:

*ngIf="i==0 || firstLetter(game.name) != firstLetter(games[i-1].name)"

This adjustment is necessary because when the initial item is loaded, i==0, causing games[i-1] to be undefinded which leads to an error being thrown.

Answer №2

When using *ngIf, ensure to modify the following:
firstLetter(game[i-1].name)
to
firstLetter(games[i-1].name)

Take note of changing game to games.

The current action with firstLetter(game[i-1].name) involves attempting to access the property [i-1] of the GameView-objects (game), which does not exist.

By adjusting it to firstLetter(games[i-1].name), you will retrieve the GameView-object from the games-array at index

[i-1]</code and then access that object's <code>name
property.

You should also account for when i is equal to 0, as

games[i-1]</code becomes <code>games[-1]
, resulting in undefined since there is no element at index -1. Following @Duannx's advice, add i == 0 || at the beginning of your *ngIf like this:

*ngIf="i == 0 || firstLetter(game.name) != firstLetter(games[i-1].name)"

If the initial statement, such as i == 0, is truthy with the use of ||, the second statement will not be evaluated, preventing an attempt to access games[-1].

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