User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.8 Safari/534.7 Build Identifier: Say in an extension I have window variable. To get the user's view of it: var win = window.wrappedJSObject; Now why does this not work most* of the time: var a = win.Object; var b = new a(); var c = b instanceof a; Instead of working, it is throwing "invalid 'instanceof' operand"? http://groups.google.com/group/mozilla.dev.platform/browse_thread/thread/dc708c6387431221/0f0fee45103c341f Reproducible: Always
7 years ago
Is this a regression? Did this work in Firefox 3.6 etc?
Does not work on Firefox 3.6
Ok, thanks for testing! Not blocking 2.0 on this issue then, but would most certainly consider a fix if one shows up.
Just a note: I don't know what environment the Error Console provides, so I can't speak to that. But within an extension, wrappedJSObject exists and is necessary. I am certainly all for having the issue fixed though!
var win = top.opener.gBrowser.selectedBrowser.contentWindow; var a = win.Object; alert(a) => undefined, so comment 4 is testing something else.
I tried this in the web console and it seems to work as expected. Without a test case I will wfm this.
OK, just curious though... what "web console" are you using to test?
pcwalton showed me how to get hold of a contentWindow through a web console opened for about:blank (which should be chrome). Any better way to try this?
Just that it needs to be from chrome priv code. Do you have Chromebug installed?
No, but about:blank is chrome so the web console is chrome. I used Components.interfaces and .classes, so I am pretty sure I was running with chrome privileges.
Umm, OK. But I have no idea what context that is bound to, so I don't trust it. It likely is bound to about:blank which is inside <xul:browser> which negates the problem. You are already inside the context, not reaching in from outside. Anyhow, in Chromebug, with the browser.xul context: win = window.document.querySelector("browser").contentWindow.wrappedJSObject; var a = win.Object; var b = new a(); var c = b instanceof a; c >>> false
I will try that.
If: win = window.document.querySelector("browser").contentWindow.wrappedJSObject doesn't work, then that trick to get to chrome won't be much help. Perhaps this and https://bugzilla.mozilla.org/show_bug.cgi?id=620486 are related? Thanks for taking a look at it. :) UCI Alumni here, BTW ;)
Hey Steve, sorry, I will need some additional instructions here. I can't even get chromebug to open properly with beta8. Its window is all out of whack. I have the extension installed. What exactly do I do and where exactly do I have to try the test case? First time chromebug user here, so pardon my slowness.
about:blank may or may not be chrome, depending on the exact way it's loaded and a few other things....
No problem. You need to start Firefox with -chromebug and have firebug installed. I'm guessing you are using FF4, which means you should use SVN and not a downloaded copy of either. Sorry about that, but FF/JSD has changed a bit in the last few weeks and FB to match. svn checkout http://fbug.googlecode.com/svn/ <mypath>\firebug-repo Then create two text files in your <profile>/extensions folder: firstname.lastname@example.org and email@example.com In firstname.lastname@example.org put: <mypath>\firebug-repo\branches\firebug1.7 In email@example.com put: <mypath>\firebug-repo\chromebug\branches\chromebug1.7 At least that way you can always have a profile to play with those tools should the need arise. Otherwise I need to figure out how to build them.
OK, ignore the a7 version #s of both, but those two files should work. They *might* even update correctly when a8 does come out. Assuming you got them installed either via SVN checkout or via the attachments, then open Firefox with -chomebug. For me I do this: "C:\Program Files (x86)\Minefield\firefox.exe" -chromebug -purgecaches Then in Chromebug I think there is a first run text you should get rid of, then click on the Console tab panel. browser.xul I think is selected by default.
I tried it. Same here. win.Object is undefined, thats why instanceof fails. Can you confirm that?
>>> win.Object Object() No failure for me.
Ok then I am still doing something wrong. I installed chromebug, started it, and selected one of the browser.xul contexts. What is different for my setup? And how did you get win exactly? win = window.document.querySelector("browser").contentWindow.wrappedJSObject; right?
Right. Should grab the first browser object it finds. Oh. tabbrowser is the better bet. win = window.document.querySelector("tabbrowser").contentWindow.wrappedJSObject
It should show the URL of the content page... >>> window.document.querySelector("tabbrowser").contentWindow Window prerelease.html What do you see for that?
Created attachment 503394 [details] capture Sorry, its just not behaving the same way for me. Any chance you can turn this into some test case I can run without firebug/chromebug? Some standalone xpi? Anything, really.
Ok, tabbrowser might have worked. Trying with that.
Ok I think I can reproduce this now.
win = window.document.querySelector("tabbrowser").contentWindow.wrappedJSObject; var a = win.Object; var b = new a(); var c = b instanceof a; console.log(c); // this bug console.log(win.Object == win.Object); // other bug
I think you might like to look at Bug 620486, since I guess it is possible that instanceof does some checks through wrappers and expects the equality tests to be accurate.
(In reply to comment #16) > Hey Steve, sorry, I will need some additional instructions here. I can't even > get chromebug to open properly with beta8. Its window is all out of whack. I > have the extension installed. What exactly do I do and where exactly do I have > to try the test case? First time chromebug user here, so pardon my slowness. It's not you: none of FF4.0b7 or b8 will work. b9pre tracemonkey is the first one that behaves, trunk perhaps if some of tracemonkey has been merged (we don't know).
I am using TM trunk. Thanks for helping out with hunting this down. We will do our best to get this fixed asap.
jjb, you were right. This is a dup of the win.Object != win.Object bug. We walk the proto chain and compare whether any of the objects along the chain matches the left hand side of the instanceof, but since we don't properly maintain identity, that match doesn't succeed. So back to fixing the other bug, and with that this one should go away. I will dup as soon we have proof for my theory.
Hopefully that is true... which is why I put: console.log(win.Object == win.Object); // other bug in comment #32. However.... this bug is also in Firefox 3.6, while the other is not.
BTW: I added my own instanceof to Firebug that does the proto chain walking itself rather than rely on the one in the language itself. That worked for 3.6. But because of the other bug, it does not work for 4.0. And that was the backup plan until this got fixed. I think the other one is more important though. And maybe this one will fix itself once the other is fixed. But I would not close it as a duplicate just yet, considering the problem is also in 3.6, and there is no test that passes yet. If you want to test Fx3.6, you can install Firebug and Chromebug in another profile as described in comment #18, but change the paths in the text files to end in 1.6 instead of 1.7.
We fixed this in the patch for bug 620486.