Change Fontsize of Label on Android smartphone

I tried this code to change the fontsize of a label. It works in Chrome browser on an pc but not on a android smartphone.

Slider1.onclick = function() {
  s= Slider1.value; = s  +  "px";

What do I have to change?

best regards

OK I found it. The slider does not react on “onclick”. It reacts on “onchange”