2.1.161 [ECMA-262-1999] Section B.2, Additional Properties
Some implementations of ECMAScript have included additional properties for some of the standard native objects. This non-normative annex suggests uniform semantics for such properties without making the properties or their semantics part of this standard.
JScript 5.x implements all of the properties listed in [ECMA-262-1999] section B.2. However, in some cases identified below, the definition used by JScript 5.x differs from that in the base specification.