for-in statement: null and undefined

Kent Hansen khansen at
Thu Jul 3 08:42:53 PDT 2008

In the current public ES4 reference implementation [1], iterating over
null and undefined is a no-op instead of a TypeError, which is in line
with the proposal at [2] (which points out that existing web browsers
already do this). However, the most recent ES3.1 draft [3] does not
incorporate this change. It's not mentioned in Douglas Crockford's
recommendations for modifications to ES [4] either, nor in the proposed
incompatibilities [5]. So my question is, will this change be part of
ES3.1 or not (doesn't it have to, for ES4 compatibility's sake)? I can't
find a discussion of this issue anywhere.

By the way, in the ES4 reference implementation, iterating over strings
is a no-op as well; implementation bug, or are string properties not
enumerable in ES4? "X".hasOwnProperty(0) returns false, too.



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