Assign Return Value from Arcade Expression to Variable in JavaScript

[LeviCecil]

I have an app based on this JS template for hovering over features. I want the title of the dialog to come from an Arcade expression. I set up a plain text script: 

<script script type="text/plain"  id="featureLabel">
    
    
    var siteName = "$feature.SiteName";
        var commonName = "$feature.Common_Name"; 
        var label = When(IsEmpty(commonName),siteName,commonName);
       return label;
    
  </script>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

I want to assign the return value of this script to a variable. I tried to create a label class based on this example:

var labelArcade =  document.getElementById("featureLabel").text;

        var label = new LabelClass({
      labelExpressionInfo: {
        expression: labelArcade
      }
      
    });‍‍‍‍‍‍‍‍

but var label just prints out [object Object]. Is there a way to just get the return value and assign that to a variable? I know how to do this in Python, but I'm going in circles on this one.