How to change Font-Family of all elements Dynamically?

Ionic Framework ionic-v3
1

Hi Everyone,

I am trying to change the fontfamily of the app when user taps a button by using this code

this._renderer.setStyle(document.body,“font-family”,“muller”);

but the problem is it is changing the font family of body alone not its decedents like ion-app etc etc are using Roboto, kindly tell me a way to accomplish this.

Thanks,
Dinesh Raja