en.javascript.info/1-js/4-data-structures/3-string/2-check-spam/solution.md

To make the search case-insensitive, let's bring the stirng to lower case and then search:

function checkSpam(str) {
  let lowerStr = str.toLowerCase();

  return lowerStr.includes('viagra') || lowerStr.includes('xxx');
}

alert( checkSpam('buy ViAgRA now') );
alert( checkSpam('free xxxxx') );
alert( checkSpam("innocent rabbit") );