Update overview.md

Added content to Data Element Changed section to include that the event type polls every one-second for a value.

Author: rossweale

help/tags/extensions/client/core/overview.md

@@ -120,7 +120,7 @@ The event triggers if a custom event type occurs. Named JavaScript functions tha
 
 #### Data Element Changed
 
-The event triggers if a specified data element changes. You must provide a name for the data element. You can select the data element by either typing its name into the text field, or selecting the data element icon to the right side of the text field and choosing from a list provided within the dialog that appears.
+The event triggers if a specified data element changes. You must provide a name for the data element. You can select the data element by either typing its name into the text field, or selecting the data element icon to the right side of the text field and choosing from a list provided within the dialog that appears. The Data Element Changed also polls every one-second for a value.
 
 #### Direct Call {#direct-call-event}
 
@@ -882,4 +882,4 @@ It is a wrapper for common JavaScript operations. It receives a data element as
 
 * Basic string manipulation (replace, substring, regex match, first and last index, split, slice)
 * Basic array operations (slice, join, pop, shift)
-* Basic universal operations (slice, length)
+* Basic universal operations (slice, length)