Java script Support in ACS

Hi Experts,

Just need to understand what level of Java script we can use in the content blocks in ACS.

const RSS_URL = '<<URL>>';
fetch(RSS_URL)
  .then(response => response.text())
  .then(str => new window.DOMParser().parseFromString(str, "text/xml"))
  .then(data => {
    console.log(data);
    });

Can i use above code in content block where i can call the rest API, use the values and render in email?

Or any other way to call rest API in ACS which returns XML RSS feed, which i can use and generate html.