Angular 6 data modification update: What you need to know

Whenever a new response is added to the array of 15 responses, I aim to dynamically update the view without requiring the page to refresh.

    addResponseToItemArray(res: DashboardInfo[]): void {
    this.item.push([]); // ERROR
    this.item.push([]); // WARNING
    this.item.push([]); // INFORMATION
    this.item.push([]); // OK
    let element;
    while ((element = res.pop())) {
        let index: number;
        if (element.level === "ERROR") index = 0;
        else if (element.level === "WARNING") index = 1;
        else if (element.level === "INFORMATION") index = 2;
        else index = 3;
        if (element.path !== undefined) {
            if (this.featuresFlag.visibleFeatures.includes(element.path)) {
                this.item[index].push(element);
                this.item = this.item.slice();
            }
        }

    }
}

Answer №1

The answer provided by @pascalpuetz is correct. Here's a more detailed example:

Let's assume we have an interface for a card like this:

interface Card {
  id: string; // unique identifier for the card
  type: 'error' | 'success' | 'warning';
  message: string;
  delay: number;
}

You can track cards using a unique property of the Card object such as the id.

trackCardsById(index: number, card: Card) {
  return card.id;
}
<div *ngFor="let card of cards; trackBy:trackCardsById " class="card" [ngClass]="card.type">
  {{card.message}}
</div>

Alternatively, you can track cards by their position in the list:

trackCardsByIndex(index: number, card: Card) {
  return index;
}
<div *ngFor="let card of cards; trackBy:trackCardsByIndex " class="card" [ngClass]="card.type">
  {{card.message}}
</div>

For a working example, check out this link.

Answer №2

To optimize your Angular template rendering, utilize the *ngFor trackBy attribute.

<div *ngFor="let i of items; trackBy: trackByFn"></div>

In your component.ts file, include the following:

trackByFn(index, item) {
  return index; // or item.id
}

For a detailed explanation and example, visit:

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