NgClass

Adds and removes CSS classes on an HTML element.

The CSS classes are updated as follows, depending on the type of the expression evaluation:

• string - the CSS classes listed in the string (space delimited) are added,
• Array - the CSS classes declared as Array elements are added,
• Object - keys are CSS classes that get added when the expression given in the value evaluates to a truthy value, otherwise they are removed.

          
<some-element [ngClass]="stringExp|arrayExp|objExp|Set">...</some-element><some-element [ngClass]="{'class1 class2 class3' : true}">...</some-element>
        

For more simple use cases you can use the class bindings directly. It doesn't require importing a directive.

          
<some-element [class]="'first second'">...</some-element><some-element [class.expanded]="isExpanded">...</some-element><some-element [class]="['first', 'second']">...</some-element><some-element [class]="{'first': true, 'second': true, 'third': false}">...</some-element>