fetch() in CEP Panel - can't get it to work

Hi All;

Anyone have an idea what the issue is here with a fetch() inside a CEP:

The Fetch() code works fine in a standalone JS, but when part of a CEP, it does not - for me. The code executes all the way to "// Get Here" in the code below. Is Fetch() not an option in CEP or what did I screw up? 

"doWorkForComp() "is called from a button event   

Thanks so much for any help.

function doWorkForComp(nextLayerToBeProcessed){
     var url = 'https://randomuser.me/api/?results=10'; // Get 10 random users
   
    fetchData();
   
   } 
   
   
    function fetchData() {
      // Get here
      fetch(url)
      .then(function(response){
          return response.json();})
      .then(function(data){     
       data.results.forEach(function (person) {
         alert(person.email);
        })
    });
}