Why this JavaScript doesn't work?

How do I...?
#1 
var hostName = window.location.hostname; // Get the full hostname of the current URL
var topLevelDomain = hostName.substring(hostName.lastIndexOf('.') + 1); // Extract the top-level domain (e.g. "com", "org", "edu", etc.)


if (topLevelDomain === 'com') {
    // Top-level domain is ".com", set variable to "en"
    runtimeScene.getGame().getVariables().get('Lang').setNumber(0);
    runtimeScene.getGame().getVariables().get('myVariable').setString('en');

It should detect a top level domain and save “en” to a string if a site has “.com”