The script that generates the JavaScript DOM listings also make a number of tests on the objects that it lists, and adds a note to the pages to report pertinent results. These are the notes that are reported along with property values in the listing:-

• String concatenation [and calling toString()][ and valueOf()] threw exceptions

When attempting to generate the contents for the second column, the script generates a String from the property of the object being reported. Initially it attempts to use string concatenation - ""+object[property]. If this throws an Exception, that is reported in the notes and the script goes on to attempt to call object[property].toString(). If that throws an Exception, that fact is added to the note and valueOf() is tried.

• Comparison of value with null threw an exception

Is reported when the expression object[property] == null throws an exception.

• Consecutive reads of this property return different object references.

Having acquired a reference to a property that is typeof object[property] == "object" (or a function that can be treated as an object in the context of the browser that is being examined), the reference is compared to the value returned by re-reading the property and if objRef == object[property] does not return true then the property is assumed to return a distinct object with each read of that property and this note is included to indicate that fact.

• This property was not tested.

Is reported if the property was known to exist on the object but it was not tested (usually because interacting with the object had proved to have undesirable consequences in earlier testing).