291651 2025-04-16 15:39:56 -0700 [JSC] Iterator.prototype.reduce fails with `undefined` initial parameter 2025-04-17 08:42:52 -0700 1 1 1 Unclassified WebKit JavaScriptCore Safari 18 All macOS 15 RESOLVED FIXED InRadar P2 Normal --- 1 marcel.webkit ysuzuki keith_miller webkit-bug-importer ysuzuki oldest_to_newest 2111397 0 marcel.webkit 2025-04-16 15:39:56 -0700 The specification for this function is pretty cut and dry. "Not present" is not the same as `undefined`. > Iterator.from([]).reduce(() => false, undefined) TypeError: Iterator.prototype.reduce requires an initial value or an iterator that is not done. Chrome agrees that the result of this expression is `undefined`. 2111504 1 webkit-bug-importer 2025-04-17 05:07:10 -0700 <rdar://problem/149470140> 2111505 2 ysuzuki 2025-04-17 05:08:42 -0700 Pull request: https://github.com/WebKit/WebKit/pull/44190 2111546 3 ews-feeder 2025-04-17 08:42:50 -0700 Committed 293797@main (cc66425b1afa): <https://commits.webkit.org/293797@main> Reviewed commits have been landed. Closing PR #44190 and removing active labels.