navigator.clipboard.writeText does not work in Live Preview

I have a button that copies the content of a caption to clipboard with the below code. 

const element = document.getElementById("txtCaption");

let text = element.getAttribute("aria-label");

alert(text);

navigator.clipboard.writeText(text);

This works fines in project preview but does not work in Live Preview and poublished output. The issue is with the last line. Can anyony help please?