forEach() JavaScript Method

Does anyone have an example or a sample where the forEach() JavaScript method is used in an activity? In my case, i'm trying to loop through a set of features to assign a value from a query without having to run through a for each loop activity.

In my workflow, i'm trying to use a set feature attribute activity to set a value in a feature set, the inputs are:

Feature: =$grDeficiencyCollection.featureSet.features.forEach(items=$grDeficiencyCollection.featureSet.features)

Attribute Name: DEFICIENCYLINK (field from a rest service)

Attribute Value: =$grSectionGUID.feature.attributes.GLOBALID (value returned from an earlier query)

The result from Geocortex mobile is: "$grDeficiencyCollection.featureset.features.foreach(items=$grDeficiencyCollection.featureSet.features) Object must implement IConvertible"

Any help is appreciated.