Array.prototype.indexOf use of SameValue()

John-David Dalton john.david.dalton at
Tue Apr 28 11:34:49 PDT 2009

In the ECMA 5 RC spec I noticed that Array.prototype.indexOf
(and lastIndexOf) make use of the SameValue operation.
The spec states that (9.12)  SameValue will return true If Type(x) is
Undefined or Null.

Would this not cause an issue with 9c of the Array.prototype.indexOf spec.
"c. If SameValue(searchElement,elementK) is true,  return k.".

[1,2,null].indexOf(null) -> SameValue(null, 1) -> true, return 0.

var undef;
[1,2,undef].indexOf(undef) -> SameValue(undefined, 1) -> true, return 0.


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