Datastore Cluster Array turns into String?

I'm very new to the vCO (or maybe I should call it vRO now) and therefor also very new to javascripting and digging through the API, so I apologize if this is a bit of a noob question.

I'm running below script to find the datastore cluster of a host cluster with most available space.

However, I also want to check for text in the name of the datastore. For this I use indexOf.

If indexOf finds any matches it should add the DSC (or pod) to an array.

But it seems that this operation turns my array into a string.

Because this is a new environment I only have one DSC connected to the hosts cluster, but I still think it should be able to be an array with only one value?

// Find Cluster and related variables

var hostarray = System.getModule("com.vmware.library.vc.cluster").getAllHostSystemsOfCluster(inCluster);

host = hostarray[0];

pool = inCluster.ResourcePool;

var tier = "High";

// Find Datastores in Cluster

var datastores = host.datastore;

// Find Datastore Clusters in Cluster

var storagePods = new Array();

var storagePodNames = new Array();

for (d in datastores){

     if (datastores[d].parent.vimType == "StoragePod"){

          if (storagePodNames.indexOf(datastores[d].parent.name) <= -1){

               storagePodNames.push(datastores[d].parent.name);

               storagePods.push(datastores[d].parent);

          }

     }

}

System.log("storagePods:" + storagePods[0].Summary.freeSpace);

// Find Datastore Clusters matching the tier

var podTierArray = new Array();

for each(var pod in storagePods){

     if(pod.name.indexOf(tier) >= 0){

          podTierArray += pod;

     }

}

// podTierArray becomes a string instead of array after above operation :((((

System.log("podTierArray:" + podTierArray[0]);

System.log("podTierArray:" + podTierArray);

Here is the output of above script:

[2015-02-27 12:24:27.307] [I] storagePods: 4497773428736

[2015-02-27 12:24:27.308] [I] podTierArray: D

[2015-02-27 12:24:27.310] [I] podTierArray: DynamicWrapper (Instance) : [VcDatastore]-[class com.vmware.vmo.plugin.vi4.model.VimDatastore] -- VALUE : Datastore<datastore-386>'Datastore01-High'

I'm guessing "D" is the first character of the string (which should be an array) which is also proven by the third row of the output where I print the entire string.

Because this now is a string I can't use it as an object anymore either, for example "podTierArray.Summary.freeSpace" will give me an error that it is an undefined property.

Also, as you can see earlier when I use the variable "storagePods" this is an array before I run the podTierArray operation.

Why would it suddenly become a string instead of an array of objects?