What is the purpose of trackBy in Angular's ngFor?

What is the purpose of trackBy in Angular's ngFor?

The trackBy function in Angular's ngFor helps optimize rendering by tracking items in a list. It allows Angular to identify which items have changed, been added, or removed, improving performance.

Can you give me an example of how to use trackBy?

Sure! Here's a simple example: In your component, define a method like trackById(index: number, item: any): number { return item.id; }. Then, in your template, use it like this: <div *ngFor='let item of items; trackBy: trackById'>{{ item.name }}</div>.

What happens if I don't use trackBy?

If you don't use trackBy, Angular will re-render the entire list whenever it detects a change, which can lead to performance issues, especially with large lists.

Are there any best practices for using trackBy?

Yes! Always use a unique identifier for tracking, like an ID. Avoid using index as it can lead to issues when items are reordered.