angular2 NgFor only supports binding to Iterables such as Arrays

in case you are trying to iterate on an object:

  <div *ngFor="let location of locations | keyvalue">
       {{location.key}} - {{location.value | json}}
  </div>

KeyValuePipe Documntation

Generally speaking, the error means you are trying to iterate on an object instead of array or observable.

It looks like you want

<li *ngFor="let item of menuItems.children">
{{item}}
</li>