Angular2 *ngIf check object array length in template

Question

Refered to https://angular.io/docs/ts/latest/guide/displaying-data.html and stack How to check empty object in angular 2 template using *ngIf still getting syntax error self context undefined. If I remove *ngIf condition then I am getting values in teamMembers if I push some value into it so I can access values in teamMembers.

my teamMember object is [ ] array i am trying to check condition array is empty by size.

Tries :

<div class="row" *ngIf="(teamMembers | json) != '{}'">

and

<div class="row" *ngIf="teamMembers.length > 0"> //Check length great than
                                                 throwing syntax error
            <div class="col-md-12">
                <h4>Team Members</h4>
                <ul class="avatar" *ngFor="let member of teamMembers">
                    <li><a href=""><gravatar-image [size]="80" [email]="member.email"></gravatar-image></a></li>
                </ul>
            </div>
        </div>

Component :

@Component({
selector: 'pbi-editor',
})
export class AppComponent implements OnInit {
teamMembers: User[];

Any help would be great.

Answer 1

<div class="row" *ngIf="teamMembers?.length > 0">

This checks first if teamMembers has a value and if teamMembers doesn't have a value, it doesn't try to access length of undefined because the first part of the condition already fails.

Answer 2

You could use *ngIf="teamMembers != 0" to check whether data is present

Answer 3

You can use

<div class="col-sm-12" *ngIf="event.attendees?.length">

Without event.attendees?.length > 0 or even event.attendees?length != 0

Because ?.length already return boolean value.

If in array will be something it will display it else not.

Answer 4

Maybe slight overkill but created library ngx-if-empty-or-has-items it checks if an object, set, map or array is not empty. Maybe it will help somebody. It has the same functionality as ngIf (then, else and 'as' syntax is supported).

arrayOrObjWithData = ['1'] || {id: 1}

<h1 *ngxIfNotEmpty="arrayOrObjWithData">
  You will see it
</h1>

 or 
 // store the result of async pipe in variable
 <h1 *ngxIfNotEmpty="arrayOrObjWithData$ | async as obj">
  {{obj.id}}
</h1>

 or

noData = [] || {}
<h1 *ngxIfHasItems="noData">
   You will NOT see it
</h1>