The behavior there is a result of the 'new' operator. typeof new String("foo") is specified to be "object", and it is extensible (String("foo") is not). Both ==

The behavior there is a result of the 'new' operator. typeof new String("foo") is specified to be "object", and it is extensible (String("foo") is not). Both == and === on two object-types return true if both refer to the same thing. More generally, when two types are the same, == has the same behavior as ===.