vRAWaitForIP.js

//inputs: string uuid, number timeout (minutes), number interval (polling interval in seconds)
//output: string actionResult (IP address)
//returns IP address or throws timeout exception
if (uuid == null) throw "vRA/vCAC VM IaaS UUID is required";

var remainingTime = timeout * 60; //convert timeout minutes to seconds

while(remainingTime > 0) {
  try {
    if (vm == undefined || vm == null) { //get VM once
      var vm = Server.findForType("vCAC:VirtualMachine", uuid);
      if (vm == null) throw "VM not found for UUID: " + uuid; //continue to wait for VM by UUID
      var hostId = vm.getEntity().hostId;
    }
    if (host == undefined || host == null) {
      var host = Server.findForType("vCAC:VCACHost", hostId); //get IaaS host once
      if (host == null) throw "IaaS host object could not be found by id: " + hostId;
    }
    var vCACVmExtendedProps = System.getModule("com.vmware.library.vcac").getPropertiesFromVirtualMachine(host, vm);
    if (vCACVmExtendedProps == null) throw "No properties yet for VM";
    var address = vCACVmExtendedProps.get("__datacollected_ipaddress"); //get IP
    if (address == null) throw "IP Address not present yet"; //continue to wait for IP address
    System.log("Found IP Address for VM with UUID '" + uuid + "'  on vRA IaaS host '" + host.name + "': " + address);
    return address;
  }
  catch (e) {
    System.log(e);
    System.log("Waiting on IP address...");
    System.sleep(interval * 1000);
    remainingTime -= interval;
    if (remainingTime <= 0) throw "Timeout waiting for IP address on VM: " + vm.name;
    continue; //continue in while loop
  }
}
throw "Timeout waiting for IP address on VM: " + vm.name;

Get the vm and the IaaS host once, poll for new copy of extended props to see if ipaddress is in them yet.
If anything we need is not present, throw an exception with a helpful message and wait for our polling interval and try again.
Do this until you find the ip address or run out of time.