22509 2013-06-28 18:17:03 +0000 Some way to express array as readonly and fixed length 2016-10-21 21:15:34 +0000 1 1 1 Unclassified WebAppsWG WebIDL unspecified PC All RESOLVED WONTFIX [v1] P2 normal --- 1 w3c cam bruant.d bzbarsky d mike public-script-coord waldron.rick public-webapps-bugzilla oldest_to_newest 90002 0 w3c 2013-06-28 18:17:03 +0000 Would be nice if the spec provided some way in IDL to express that an array is readonly and/or fixed length. http://dev.w3.org/2006/webapi/WebIDL/#idl-array [[ Arrays can also be designated as being read only. ]] 90004 1 waldron.rick 2013-06-28 20:54:35 +0000 Is frozen-ness insufficient? 90006 2 bruant.d 2013-06-28 21:39:41 +0000 (In reply to comment #0) > Would be nice if the spec provided some way in IDL to express that an array > is readonly and/or fixed length. Are there cases of fixed length in the platform? (In reply to comment #1) > Is frozen-ness insufficient? I don't think there is a WebIDL way to express that an object is frozen yet (though I agree that could be a solution here) 90015 3 bzbarsky 2013-06-29 02:08:42 +0000 frozen-ness is not the right thing. The point of readonly or fixed-length arrays is to return an arraylike object to a caller with the following properties: 1) The caller can read things from the arraylike. 2) The caller cannot write things to the arraylike. 3) The _callee_ can write things to the arraylike as needed. Most cases where you'd not want the callee to later modify the object just want pass-by-value semantics and actual JS arrays. 90016 4 waldron.rick 2013-06-29 02:39:46 +0000 (In reply to comment #3) > frozen-ness is not the right thing. > > The point of readonly or fixed-length arrays is to return an arraylike > object to a caller with the following properties: > > 1) The caller can read things from the arraylike. > 2) The caller cannot write things to the arraylike. > 3) The _callee_ can write things to the arraylike as needed. > > Most cases where you'd not want the callee to later modify the object just > want pass-by-value semantics and actual JS arrays. Got it, thanks for the clarification 127906 5 d 2016-10-21 21:15:34 +0000 We used to have this, in T[]. It was removed in favor of FrozenArray and a general movement toward a different pattern of returning a new frozen array object each time. I think we won't go back to a T[]-like world, unless ES somehow add readonly-but-not-immutable arrays as a first-class concept.