<a [ngClass]="{'class1':array.status === 'active','class2':array.status === 'idle','class3':array.status === 'inactive',}">
[ngClass]="{'my-class': step === 'step1'}"
<section [ngClass]="{'class1':condition1, 'class2': condition2, 'class3':condition3}" >
[ngClass]="{1:'my-class1',2:'my-class2',3:'my-class4'}[step]"