That is for ionic.js (ionic v1). You marked this thread with the category ionic (ionic v2+). These versions are very different. You cannot use v1 code in v2+ that easy.
Maybe this fits your use case: How to enlarge font size of text on button click
That is for ionic.js (ionic v1). You marked this thread with the category ionic (ionic v2+). These versions are very different. You cannot use v1 code in v2+ that easy.
Maybe this fits your use case: How to enlarge font size of text on button click