NgClass binding from TS

  ANgular ngclass binding

<tr  *ngFor="let dm of extradomain ; let i = index; let first = first;let last = last;" [ngClass]="{ bg_success: first, bg_primary: !first, bg_danger : dm.domainStatus }">

in the above code for first tr bg_success class will applay. if it is last or not first bg_primary will apply.