I am working on a helper library called Ozai to make web workers easier, but am running in to a problem in firefox. I create a web worker from a URL Blob and attempt to post this payload to it:
msg = {
"id":"0fae0ff8-bfd1-49ea-8139-3d03fb9584e4",
"fn":"fn",
"args":[100,200]
}
Using this code:
worker.postMessage(msg)
But it throws a DataCloneError exception. It looks like Firefox's implementation of structured cloning is failing on a very simple object. The code runs without problems on Chrome and Safari, but fails in the latest version of Firefox. Am I missing something here? How do I get around this (preferably without stringifying the payload)?
Here's a fiddle: http://jsfiddle.net/V8aCy/6/
And a pic of Firelord Ozai:
You're trying to call postMessage with an object that has a property referencing arguments. That doesn't work because data has to be transferable, which means either fully JSON-serializable or implementing Transferable (e.g. ArrayBuffer), which arguments is not.
Use Array.prototype.slice.call(arguments, 0) to convert arguments into an array, which can be serialized (cloned) if the contents are OK.
Corrected fiddle.
Related
I'm trying to code an extension to Firefox for the first time and I have a problem with the prefmanager.
var prefManager = Components.classes["#mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefBranch);
var updateintervall = prefManager.getCharPref("extensions.traffic.updateintervall");
After the second line of Javascript code my extension seems to stop working. The following codelines won't be excecuted anymore... What am I doing wrong?
The nsIPref* API expects preferences to already exist when using the get*() functions. When trying to get a preference that does not and exception will be thrown.
Also, the API may throw if you try to read e.g. an existing numerical preference as a string.
You can try/catch exceptions of course.
You might want to add default preferences to your XUL-based add-on, to not having to try/catch for non-existing prefs.
SDK users should have a look at the simple-prefs and/or preferences/service APIs.
Aside: These days you'll want to use the cached Services.prefs to access nsIPref*.
TypeError: Unable to get value of the property 'childNodes': object is null or undefinedundefined
After making a long list of modifications to my application in order to support IE8, including:
running all of the views in their compiled form through W3C validator, setting up xdomain.js proxy to support CORS API calls, making some general restructures, etc.
I was very disappointed to find out that IE8 still throws this weird error at me, while IE9 works perfectly fine.
Making changes to the Angular-seo package to prevent it from running when the client is an IE browser.
Any ideas on what can it be?.
Make sure that all your tags are closed properly. I just spent hours trying to figure out what the problem was, until I noticed this in my code:
<span>some text<span>
I finally realized I didn't close the <span> tag properly. After that everything just worked.
Without the code you are running it is a bit difficult. However there is a command to use for debugging. First you need to identify which variable might not contain an object [i.e.
"object is null or undefined"].
For example, parent, then you can use
//next look to see if parent is something
if('undefined'==(typeof parent)) alert("variable empty:parent");
Once you find something that is empty that you are expecting to be an object then you can go trace back from there. Also use a browser debugged tool, to identify the line number of the error.
Often if using the child nodes, you may not have the right level or you need to access as an array i.e. you need something like.
parent.childNodes[0].childNodes[0].value
In IE you are also dealing with unsupported functions. So getElementById will work but some other similar ones do not. Again typeof can be useful.
//next ensure function supported
if( 'undefined'==(typeof document.getElementsByClassName) ){
alert("Not Supported"); // notice ^ no () required here
//...add code to handle differently when not supported
}
This may reveal if you can use a function
IE8 is so old and non-standards compliant it doesn't support childNodes[]. http://quirksmode.org/dom/core/#t70
Company recently upgraded to Flash v11.8.800.168 and a flash movie which is loaded using SWFObject (1.1) is not working correctly in Internet Explorer (Firefox works fine). The movie is loaded dynamically using a jquery document.ready method using the "new SWFObject(...); so.write("ID")" method (again SWFObject 1.1).\
The movie on load calls a JavaScript function (which is built dynamically using server scripting). The function is being called correctly as checked by a debugger. The JavaScript function calls a method in the flash movie passing it some XML (which is used to render some user and navigation items).
Something like this:
function calledFromFlash() {
document.getElementById("FlashMovie").renderUsingXml('<?xml version 1.0"?><lotsofxml></lotsofxml>');
}
Like I said, this all works still in Firefox with the new Flash version.
When I step through the function above, using step into with the IE Debugger, I get the following steps:
function anonymous() {
return eval(this.CallFunction("<invoke name=\"renderUsingXml\" returntype=\"javascript\">" + __flash__argumentsToXML(arguments, 0) + "</invoke>"));
}
At this point, I checked the arguments variable and it contains the XML as one would expect. After the next step into, I get this:
try { __flash__toXML(calledFromFlash(undefined)); } catch (e) { "<undefined/>"; }
At this point the debugger is already on the catch, yet one more step into take the code into the "<undefined/>" section and I can see that e is Object Expected
What I've tried:
Static implementation without SWFObject. This works. But then Firefox doesn't process the XML properly (and it seems to be the same issue as IE)
Upgrading to SWFObject 2.2. Using dynamic implementation it fails still. Using static implementation it works in IE but not Firefox
This is NOT my flash movie, the source is... well, I don't know. The guy that wrote it has left the company. That said, this seems like such a crazy issue.
My proposed fix is simply to use SWFObject for Firefox and use a static implementation for IE, but I really want to know what is wrong.
This was caused by a bug in Flash Player 11.8.800.168. It has been fixed in 11.8.800.175.
Bug fixes:
3630443 - [External][Windows][IE] ExternalInterface.call() method with non-ASCII text as a parameter corrupts the characters on the Javascript side
I have implemented an MSR OPOS ActiveX control for use in an IE-based web application. I have tested the device and it works; however, I'm trying to port the VBScript code found here to JavaScript for easier maintainability.
I'm having trouble binding to the DataEvent with JavaScript though -- when I put the card to the reader, the data definitely appears to take, as I can query the object directly through the console with ReaderControl.Track1Data and see that there is in fact data there.
In the VBScript version, there seems to be a method called [control]_DataEvent that you can simply override in order to bind to the event. I have tried ReaderControl.attachEvent("DataEvent", function() { alert(ReaderControl.Track1Data); }), which does seem to work, for some reason, only when subsequently set ReaderControl.DataEventEnabled = true;.
Any ideas?
I'm using JSON.Stringify and JSON.parse everywhere and it works fine with Firefox. It's working no more with IE9 nor does it work in IE8. What can I do?
JSON.stringify starts with a lower-case s. Both stringify and parse are available in IE8+, but only in standards mode.
Prepend your document with <!DOCTYPE html> if you're currently using quirks mode. Also, watch the capitalization of the JavaScript methods you call - all built-in ones start with a lower-case character.
why do you want to depend on the browser having the object instead just include the script file by Douglas Crockford.. You can find the minifed file here: http://www.json.org/js.html
Once imported you dont have to worry abt the method existing in a browser.
For an alternative, in a scenario where you might need to run in strict mode for whatever reason (I have another library that includes "use strict"), you can look here: https://github.com/douglascrockford/JSON-js. I modified this to check first if JSON is undefined, and only generate the function JSON.parse if it is:
if (typeof JSON === "undefined") {
var JSON = {
parse: <insert value of json_parse from library here>
};
}
My issue was application code not working in IE9 (strict mode being used by a participating library, I believe). That solved the problem for me.
the mere issue is, that sending UTF-8 headers will invalidate the JSON (IE doesn't/didn't like that). as the issue is described, that might still apply for IE9... once wrote a how to, a few years ago. adding JSON support to a browser which can parse native JSON is probably not the optimal solution, since it produces useless overhead - only because failing to deliver the JSON in the expected format.