Help with java script code in Announcement banner


I write code that add to element class name, but it’s not work from the banner,
I need help with this please,

this is the banner code:
console.log(“Shani: Start add show class”);
var popup = document.getElementById(“myPopup”);
console.log(“Shani: End add show class”);

the html code that write in script field in JIRA I can’t upload, i get blocked becouse I am new here,


Shani Levi