613706 - Object.watch breaks programs that test Object.hasOwnProperty

Status: RESOLVED DUPLICATE of bug 394964

(Core :: JavaScript Engine, defect)

Description

[John J. Barton]

Try this in the Firebug console or a Web page

var anObj = {};
anObj.watch("foo", function say(id, oldV, newV){});
if (anObj.hasOwnProperty('foo'))
  console.log("buggy");
else
  console.log("golden");

It's a shame because programs that logically know they never set properties to 'undefined' break  when you add 'watch' to debug them.

Similarly for (p in anObj) reports 'foo' but says it is 'undefined'.

Comment 1

[Sebastian Zartner [:sebo]]

Isn't that a duplicate of bug 394964? As soon as watch() doesn't add properties anymore, hasOwnProperty() should be false.