Subject: DOMParser in mfcembed - msg#00011

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instanceof/prototype problem with objects created in different frames

I am currently exploring prototype based inheritance when scripting with frames and using objects created in one frame in script in another frame. Mozilla (tested with 1.7.3) shows an odd behaviour when applying the instanceof operator on an object created in one frame and a constructor function created in another frame, it yields instanceof as true but when you check for a property defined on the prototype then the property is not found with the in operator. A test case using Date objects is here: http://home.arcor.de/martin.honnen/javascript/200412/test2004120601.html another test case that deals with DOM object (document object in that case) is here: http://home.arcor.de/martin.honnen/javascript/200412/test2004120502.html From my understanding it is correct that an object created in one frame doesn't have the properties defined on the prototype of a constructor function created in another frame as that prototype doesn't sit in the prototype chain of the object but then I wonder why Mozilla gives instanceof as true for that object and that constructor function. It seems like a bug to me but before I file one I thought I would ask here for opinions. IE 6 and Opera 7.50 give the same results as Mozilla (for the first test case) for the 'in' operator checks but then (in my view consistently) yield false for the instanceof check for the object created in one frame and the constructor function created in another frame where Mozilla yields true. In case the above is not detailed enough to understand what I am after I will explain a bit more now: with JavaScript you can add properties/methods to the prototype of constructor functions e.g. Date.prototype.foo = function () { ... }; and then objects created with that constructor function 'inherit' those properties/methods as that prototype object sits in the prototype chain an object is hooked up to. In JavaScript 1.5 (or other ECMAScript edition 3 implementations) there is also the instanceof operator e.g. object instanceof functionObject that returns true or false depending on (in my understanding) the prototype of the functionObject sits in the prototype chain of the object. Thus if you are only looking at one window/frame then if you have var date = new Date() then date instanceof Date yields true and 'foo' in date is also true. Now enter frames and scripting between frames and you have different global objects and different constructor functions like Date in each frame so consequently if you create a Date object in one frame e.g. var date = new Date() and then check instanceof on the constructor in another frame it should yield false e.g. date instanceof parent.frames.frameName.Date but in Mozilla it doesn't, I get true. Why is that? In particular as a check of properties with the in operator yields false. I think that is inconsistent, if object instanceof functionObject is true and a property/method functionObject.prototype.foo exists (the test case checks that using hasOwnProperty) the 'foo' in object needs to be true too. So what do you think, should I file a bug on Mozilla yielding true on objectCreatedInOneFrame instanceof functionCreatedInOtherFrame or do you have an explanation for that? -- Martin Honnen http://JavaScript.FAQTs.com/

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instanceof/prototype problem with objects created in different frames

I am currently exploring prototype based inheritance when scripting with frames and using objects created in one frame in script in another frame. Mozilla (tested with 1.7.3) shows an odd behaviour when applying the instanceof operator on an object created in one frame and a constructor function created in another frame, it yields instanceof as true but when you check for a property defined on the prototype then the property is not found with the in operator. A test case using Date objects is here: http://home.arcor.de/martin.honnen/javascript/200412/test2004120601.html another test case that deals with DOM object (document object in that case) is here: http://home.arcor.de/martin.honnen/javascript/200412/test2004120502.html From my understanding it is correct that an object created in one frame doesn't have the properties defined on the prototype of a constructor function created in another frame as that prototype doesn't sit in the prototype chain of the object but then I wonder why Mozilla gives instanceof as true for that object and that constructor function. It seems like a bug to me but before I file one I thought I would ask here for opinions. IE 6 and Opera 7.50 give the same results as Mozilla (for the first test case) for the 'in' operator checks but then (in my view consistently) yield false for the instanceof check for the object created in one frame and the constructor function created in another frame where Mozilla yields true. In case the above is not detailed enough to understand what I am after I will explain a bit more now: with JavaScript you can add properties/methods to the prototype of constructor functions e.g. Date.prototype.foo = function () { ... }; and then objects created with that constructor function 'inherit' those properties/methods as that prototype object sits in the prototype chain an object is hooked up to. In JavaScript 1.5 (or other ECMAScript edition 3 implementations) there is also the instanceof operator e.g. object instanceof functionObject that returns true or false depending on (in my understanding) the prototype of the functionObject sits in the prototype chain of the object. Thus if you are only looking at one window/frame then if you have var date = new Date() then date instanceof Date yields true and 'foo' in date is also true. Now enter frames and scripting between frames and you have different global objects and different constructor functions like Date in each frame so consequently if you create a Date object in one frame e.g. var date = new Date() and then check instanceof on the constructor in another frame it should yield false e.g. date instanceof parent.frames.frameName.Date but in Mozilla it doesn't, I get true. Why is that? In particular as a check of properties with the in operator yields false. I think that is inconsistent, if object instanceof functionObject is true and a property/method functionObject.prototype.foo exists (the test case checks that using hasOwnProperty) the 'foo' in object needs to be true too. So what do you think, should I file a bug on Mozilla yielding true on objectCreatedInOneFrame instanceof functionCreatedInOtherFrame or do you have an explanation for that? -- Martin Honnen http://JavaScript.FAQTs.com/

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Re: DOMParser in mfcembed

I tried to create other instance from xmlextras extension like "@mozilla.org/xmlextras/xmlserializer;1". It succeed. Don't know what's going on. Can somebody help? "Chris Du" <cheng_du2000@xxxxxxxxx> wrote in message news:cp5giv$j021@xxxxxxxxxxxxxxxxxxxxxx > Hi, guys, > > I insert the following code to a function BOOL > CMfcEmbedApp::InitializeProfiles() to parse a xml string. > But the do_CreateInstance failed. > Can somebody tell me why? > Thank you very much. > > This is just a test code for dom parser. > My final target is to let mfcembed load an xml without rendering and my > code parse the xml and load other xhtml files indicated by href in the > startup xml. > > /* my code begins */ > char szXML[] = "<?xml version=\"1.0\" encoding=\"utf-8\"?><startup> > <wallgarden> <loadinfo href=\"a.htm\"/> </wallgarden></startup>"; > nsresult rv; > nsCOMPtr<nsIDOMParser> pDOMParser; > nsCOMPtr<nsIDOMDocument> pDOMDocument; > pDOMParser = do_CreateInstance( NS_DOMPARSER_CONTRACTID, > &rv ); > > if (NS_SUCCEEDED( rv )) { > nsString str; str.AssignWithConversion(szXML); > rv = pDOMParser->ParseFromString(str.get(),"text/xml", > getter_AddRefs( pDOMDocument ) ); > > if (NS_SUCCEEDED( rv )) { > printf( "DOM parse string successful\n"); > } > else { > printf( "DOM parse of NOT successful\n"); > } > } > else { > printf( "do_CreateInstance of DOMParser failed for - %08X\n", rv ); > } > > /* my code ends */ >