This function is described as "isMacOS" in order to easily use the returned result (true / false) to do stuff accordingly. Check out the example code for a proper use of this function.

Check Current OS (Win or MacOS).jsx

function isMacOS(){
     var currentSystemOS = String($.os).toLowerCase();
     if (currentSystemOS.indexOf("mac") == -1) {
       return false
     } else {
       return true;
     }
  }

isMacOS();