Chrome appears to be up to date.
ReferenceErroris thrown when trying to assign to a primary expression that is a literal (such as
false) not an identifier.
SyntaxErrors) of unspecified type is thrown for assignments "on any value for which an early determination can be made that the value is not a Reference", though if it would happen a
ReferenceErrorwould be thrown so one might argue that the early error should be of that type as well.
While the error handling in Firefox may be excused by the ES5 or ES3 wording, the behaviour Internet Explorer throwing a runtime
SyntaxError does not match any of these. However, Microsoft plans to fix this in Chakra. For some discussion, see also https://github.com/tc39/ecma262/issues/257.