I'm experimenting with the new ES6 Symbols in Google Chrome, and after enabling "Experimental JavaScript" in Chrome Flags, I can use new Symbol() in my code.
However, when I try to run the following code:
var sym = new Symbol();
var obj = {};
obj[sym] = 'Hello, symbols';
I get the following error:
TypeError: Conversion from symbol to string
What's wrong with my code?
Thanks!
Since symbols are values, not objects, they are created by a plain function call to Symbol, not by invoking new on it. In the version of Chrome you are using, new Symbol gives you a wrapper object for such a value (i.e., you can get the actual symbol by invoking .valueOf on the result).
Since this is a common pitfall, the ES6 draft spec recently changed to disallow constructor invocation of Symbol altogether. That is, you already get an exception on the first line of your code. This change has already been implemented in V8, but hasn't made it into Chrome yet.
Related
After creating our new system in Vue with babel, I have started testing compatibility towards older devices. Our babel is transpiling the source down to es2015 together with webpack.
I have now tested with browserstack against both Ios & android. Newer OS works on both platforms. However on android phones that use the default browser, I get an error in sentry stating; Duplicate data property in object literal not allowed in strict mode It does not give me any hints on where this might be thus making the debugging process painfully hard.
The only light in the end of the tunnel I can se now is the ios part. Ios devices that run IOS < 9 states an error Attempted to redefine property 'value'. also in sentry
If I am not mistaking, the ios issue is a reworded error of the same issue?
As I read over here, I suppose 'value' might be defined twice in a object or element.
This all wraps up to the question, how does one go with finding duplicate data properties?
Can you share some of your code (just the area from a few components?)
One thing to check is inside of data(), ensure you are returning an object. This happened to me when I started out with Vue.
Example:
// component a
data () {
a: ''
}
// component b
data () {
a: '' // ERROR! Duplicate
}
This happens because the data is merged on the main Vue instance. So in this case it should look like:
// component a
data () {
return {
a: ''
}
}
// component b
data () {
return {
a: '' // ok now
}
}
Hard to make any other guesses without some code.
I had the same issue reported on a old android device, here's what i did :
We had components with both mapActions(["something"]) and a defined method something() { this.$store.dispatch('something') }
So i removed the methods declaration.
It still didn't work so I check the build main.xxxx.js on eslint
and found some "Attempted to redefine property 'value'" on something like domProps:{value:t.value,value:t.value}
Looked up the code and saw that we had components with both v-model and :value and also some checkbox using v-model and :checked.
I only kept the v-model and it works.
It also seems like the problems could come from repeated props like stated here : https://www.tutorialfor.com/blog-267252.htm
I managed to find out what line the error occurred on and found out that a plugin that I used with name Vue-numeric had created a duplicate value:
domProps: {
value: n.value,
value: n.amount
},
I had accidentally locked the plugin on a older version where this problem was present. The issue was fixed by simply updating.
Thank you #xenetics for taking your time on this issue.
Yes, this is a restriction that was only in effect in ES5 strict mode, which these environments you have apparently use. It absolutely makes sense but was nonetheless loosened in ES6 because of computed properties - see What's the purpose of allowing duplicate property names? for details. That's why babel doesn't complain about it when transpiling.
To find these (valid but nonsensical) duplicate property names in object literals in your code base, you can use a linter such as ESLint with a rule against these.
I'm using the Box SDK for .NET and just trying to get started authenticating using the Java Web Token workflow. I'm using code that's pretty much the same as the code sample that's included in the SDK's code examples.
var jwtPrivateKey = File.ReadAllText("private_key.pem");
var boxConfig = new BoxConfig(ClientId, ClientSecret, EnterpriseId, jwtPrivateKey, JwtPrivateKeyPassword, JwtPublicKeyId);
var boxJwt = new BoxJWTAuth(boxConfig);
But at that last line I'm getting an exception that says "pad block corrupted". The stack trace seems to indicate that it involves reading the private key, but I don't see what I could be doing wrong considering this is basically the same as the code sample (https://github.com/box/box-windows-sdk-v2/blob/master/Box.V2.Samples.JWTAuth/Program.cs).
Any ideas?
After re-generating the private key with Cygwin, things are working for me.
I believe what happened was I opened the private key in Notepad or something, then saved it in some format it didn't like (maybe changed encoding to UTF-8, or saved it with Windows-style line breaks).
I'm trying to create an application using the NFC (proximity) API on Windows Phone 8. When I copy the example code from the documentation, I get the following compile error...
error CS0103: The name 'Window' does not exist in the current context ...
This error is all over the internet and the common solution seems to be that it only works for native (or C++) code. However the documentation says that it works for managed or native code. How do I get the examples to work in my managed code?
In order to gain access to the active Windows.UI.Core.CoreDispatcher object, you simply need to request Windows.UI.Core.CoreWindow.GetForCurrentThread().Dispatcher.
ORIGINAL EXAMPLE CODE
// Write a message to MessageBlock on the UI thread.
private Windows.UI.Core.CoreDispatcher messageDispatcher =
Window.Current.CoreWindow.Dispatcher;
CORRECTED CODE
// Write a message to MessageBlock on the UI thread.
private Windows.UI.Core.CoreDispatcher dispatcher =
Windows.UI.Core.CoreWindow.GetForCurrentThread().Dispatcher;
The one small change makes all the examples work! Enjoy.
According to documentation (https://developers.google.com/closure/compiler/docs/api-tutorial3#externs), it seems the closure compiler should rename variables when no external declaration exists, including when using functions/variables from an external bit of code. The example they give is
function makeNoteDom(noteTitle, noteContent, noteContainer) {
// Create DOM structure to represent the note.
var headerElement = textDiv(noteTitle);
var contentElement = textDiv(noteContent);
...
}
where the textDiv function is declared in the global scope by a third-party lib of some sort. It says textDiv should be declared external to prevent renaming.
My question is - when I put this code or similar into the Closure Compiler without any extern declarations why is textDiv not renamed (which would break the code), as the documentation indicates?
The compiler assumes that calls to an undefined function are in fact calls to an external functions. Using the command line compiler, you can use --warning_level VERBOSE to have the compiler treat this condition as an error.
The Web Application is primarily built for demos and assumes this by default. While you can set a VERBOSE warning level, it will not change this functionality. See the Additional Web Service Options page for information on options. I've filed a bug report about this.
Due to the renaming algorithm for properties, undeclared properties will be renamed in a breaking way if that same property name isn't declared on an object in externs.
I am developing a Flash application (Flash Player 11 as target platform) that uses the AS3 Facebook API, which in turn uses as3corelib JSON functionality. Or at least it should do so.
However, in spite of including the latest version (.93) of the as3corelib.swc, I still get the "Error: Access of undefined property JSON". I also tried including the sources directly, to no avail.
Any ideas what I am doing wrong?
As I said, the *.swc is definitely included. As is the source code (all at the correct path).
Edit:
I have a more specific error message:
Error: Can not resolve a multiname reference unambiguously. JSON (from C:\Coding\FlashDevelop\Tools\flexsdk\frameworks\libs\air\airglobal.swc(JSON, Walker)) and com.adobe.serialization.json:JSON (from C:\flash_test\lib\as3corelib.swc)) are available.
I know that JSON is included in AIR, but I do not target AIR, so why does it try include the airglobal.swc?
Your problem is that Flash Player 11 and onwards has native JSON support, so the JSON class you are including is likely colliding with the one from as3corelib. Hence the ambiguity problem.
Try removing as3corelib entirely and see what happens.
Specify the full path to the class. Example, code:
...
var jsonData:Object = JSON.decode(loader.data);
...
will be
...
var jsonData:Object = com.adobe.serialization.json.JSON.decode(loader.data);
...