angular how to apply css conditional code example

Example 1: conditionally assign a css class angular 9

<div [ngClass]="{'message': info.priority < 10,
                 'warn': info.priority > 10 && info.priority < 20, 
                 'error': info.priority > 30}">

{{info.text}}

</div>

Example 2: Angular 8 ngClass If

[class.my-class]="step=='step1'"