A property can have zero or more attributes. The attributes control how the property is accessed both internally from inside the interpreter and externally from your script.
Here is a list of the property attributes defined by the ECMA Script standard:
|ReadOnly||The property is a read-only value. Scripts will not be allowed to change the value although the value may change from time to time if it is dependant on some host related facility.|
|DontEnum||You cannot enumerate this property with a for...in repetition.|
|DontDelete||You cannot delete this property.|
|Internal||This is an internal property, which you normally won't have any access to. It's likely it would be hidden inside the host-managed objects and inaccessible to your scripts.|
Where properties are ReadOnly, this is flagged in the documentation. Read/write access is assumed to be the default case otherwise.