• Angular

//One
[class.my-class]="step === 'step1'"
[class.text-success]="true"
//Two
[ngClass]="{'my-class': step === 'step1'}"
[ngClass]="{'text-success':true}"
[ngClass]="{'my-class': step === 'step1', 'my-class2':step === 'step2' }"
//Three
[ngClass]="{1:'my-class1',2:'my-class2',3:'my-class4'}[step]"
//Four
[ngClass]="(step=='step1')?'my-class1':'my-class2'"
[ngClass]="{
    'text-success':person.country === 'Maroc',
    'text-primary':person.country === 'France',
    'text-danger':person.country === 'Mali'
}"