Primeng - how to use styleClass?

To make things clear: the styleClass property is only an addition to the original classes of the component. That means, you always have to use the original classes in order to style the component. With styleClass you then have the possibility to address one or more components of a set of components of the same type. So, having five Togglebutton components, you can generally style those components with

.ui-togglebutton.ui-button.ui-state-active{}

If you then want to style one of those components differently, you can add the styleClass property:

<p-toggleButton styleClass="different"></p-toggleButton>

And in your css you can now address this one by:

.different.ui-togglebutton.ui-button.ui-state-active{}

Thus styleClass is not a replacement for the original selectors, it is an addition.

You can try to override o PrimeNg component doing this, eg. I was using tabMenu and worked:

<p-tabMenu styleClass="override-this"></p-tabMenu>

I suppose it will work with any PrimeNg component that accepts styleClass.

In root style.css file you just use body and then the styleClass name.

body .override-this{
  font-size: 10px;
}

I didn't test with other properties, probably if you need to change some deeper you will need to cascade like

body .override-this .ui-tabmenu .ui-tabmenu-nav and so on.