# Track By Key

The trackByKey directive will create function for \*ngFor directive and will be using as trackBy.

## Using trackByKey

An example in `COMPONENT.template.html`.

```markup
<ng-container *ngFor="
  let item of [
    { animal: '🦊' },
    { animal: '🦄' }
  ] trackByKey 'animal'">
  {{ item.animal }}
</ng-container>
```