Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.javascript > #25109 > unrolled thread

Re: Firefox Console hiding output

Back to article view | Back to comp.lang.javascript

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: Firefox Console hiding output JJ <jj4public@vfemail.net> - 2014-06-29 04:37 +0700
    Re: Firefox Console hiding output JJ <jj4public@vfemail.net> - 2014-06-29 15:02 +0700
      Re: Firefox Console hiding output Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-06-29 10:59 +0200
        Re: Firefox Console hiding output JJ <jj4public@vfemail.net> - 2014-06-29 20:48 +0700
          Re: Firefox Console hiding output Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-06-29 18:07 +0200
    Re: Firefox Console hiding output Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-06-29 10:35 +0200

#25109 — Re: Firefox Console hiding output

On 27 Jun 2014 16:49:15 GMT, Stefan Ram wrote:
>   What global objects are there? Well, ... it should be easy
>   to see! But the Console of Firefox shows me the output 
>   only from line 316 on, it seems to hide the first 315 lines.
>   (I pasted the code into the Firefox Console prompt.)
> 
> { let l = Object.getOwnPropertyNames( this );
>   let n = l.length; for( let i = 0; i < n; ++i )
>   console.log( i + ' ' + l[ i ]); }
> 
> undefined
> "316 MediaStreamAudioDestinationNode"
> "317 DynamicsCompressorNode"
> "318 DeviceProximityEvent"
> ...
> 
>   (»...« marks lines omitted by me [S.R.].)
> 
>   If one does not know this and does not print line numbers,
>   one might be led to believe that this is all there is:
> 
> { let l = Object.getOwnPropertyNames( this );
>   let n = l.length; for( let i = 0; i < n; ++i )
>   console.log( l[ i ]); }
> 
> undefined
> "MediaStreamAudioDestinationNode"
> "DynamicsCompressorNode"
> "DeviceProximityEvent"
> ...

Did that happen on all web pages, including blank HTML file?

[toc] | [next] | [standalone]

#25113

On 29 Jun 2014 00:47:16 GMT, Stefan Ram wrote:
> JJ <jj4public@vfemail.net> writes:
>>Did that happen on all web pages, including blank HTML file?
> 
>   I only ever tried it in the debugger with no web page at all:
> 
> JSON.stringify( document )
> "{"location":{}}"
> 
>   .

There are log limits enforced.
So, only the last N number of lines are displayed.

Type this in the about:config.

devtools.hud.loglimit.

[toc] | [prev] | [next] | [standalone]

#25115

JJ wrote:

> On 29 Jun 2014 00:47:16 GMT, Stefan Ram wrote:
>> JJ <jj4public@vfemail.net> writes:
>>> Did that happen on all web pages, including blank HTML file?
>> 
>>   I only ever tried it in the debugger with no web page at all:
>> 
>> JSON.stringify( document )
>> "{"location":{}}"
>> 
>>   .
> 
> There are log limits enforced.

Yes, but that is not the reason for the above result.  This is:

Object.getOwnPropertyNames(document).filter(function (name) { return 
Object.getOwnPropertyDescriptor(document, name).enumerable; })
| < Array [ "location" ]

And in Chromium:

JSON.stringify(document)
| TypeError: Converting circular structure to JSON

Object.getOwnPropertyNames(document).filter(function (name) { return 
Object.getOwnPropertyDescriptor(document, name).enumerable; })
| Array[147]

The structure is “circular” in WebCore because at least “document.body” and 
“document.body.ownerDocument” (=== document) are own, enumerable properties.

In general, it is a Bad Idea to subject host objects to JSON 
stringification.

> So, only the last N number of lines are displayed.
> 
> Type this in the about:config.
> 
> devtools.hud.loglimit.

(easier with “loglimit”)

Thanks; the default for devtools.hud.loglimit.console is 200 which explains 
the observations.  Unfortunately, there appears to be no way to disable the 
limit (neither negative values nor 0 work).

The least that should be done by Mozilla is to display a notice that the log 
limit has been reached and that output is incomplete.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

[toc] | [prev] | [next] | [standalone]

#25116

On Sun, 29 Jun 2014 10:59:33 +0200, Thomas 'PointedEars' Lahn wrote:
> JJ wrote:
> 
>> On 29 Jun 2014 00:47:16 GMT, Stefan Ram wrote:
>>> JJ <jj4public@vfemail.net> writes:
>>>> Did that happen on all web pages, including blank HTML file?
>>> 
>>>   I only ever tried it in the debugger with no web page at all:
>>> 
>>> JSON.stringify( document )
>>> "{"location":{}}"
>>> 
>>>   .
>> 
>> There are log limits enforced.
> 
> Yes, but that is not the reason for the above result.

You're right. That's just to show that there's no document loaded when he
tested the code.

>  This is:
> 
> Object.getOwnPropertyNames(document).filter(function (name) { return 
> Object.getOwnPropertyDescriptor(document, name).enumerable; })
>| < Array [ "location" ]
> 
> And in Chromium:
> 
> JSON.stringify(document)
>| TypeError: Converting circular structure to JSON
> 
> Object.getOwnPropertyNames(document).filter(function (name) { return 
> Object.getOwnPropertyDescriptor(document, name).enumerable; })
>| Array[147]
> 
> The structure is “circular” in WebCore because at least “document.body” and 
> “document.body.ownerDocument” (=== document) are own, enumerable properties.
> 
> In general, it is a Bad Idea to subject host objects to JSON 
> stringification.

I just noticed that. Why didn't JSON.stringify generate an exception?

>> So, only the last N number of lines are displayed.
>> 
>> Type this in the about:config.
>> 
>> devtools.hud.loglimit.
> 
> (easier with “loglimit”)
> 
> Thanks; the default for devtools.hud.loglimit.console is 200 which explains 
> the observations.  Unfortunately, there appears to be no way to disable the 
> limit (neither negative values nor 0 work).

Yes, disabling the log output completely doesn't seem possible. Zero or less
value settings are treated as 1. Disabling the limit on the other hand,
would mean having infinite lines, but the setting value itself is limited by
32-bit signed number.

[toc] | [prev] | [next] | [standalone]

#25117

JJ wrote:

> On Sun, 29 Jun 2014 10:59:33 +0200, Thomas 'PointedEars' Lahn wrote:
>> JJ wrote:
>>> On 29 Jun 2014 00:47:16 GMT, Stefan Ram wrote:
>>>> JJ <jj4public@vfemail.net> writes:
>>>>> Did that happen on all web pages, including blank HTML file?
>>>> 
>>>>   I only ever tried it in the debugger with no web page at all:
>>>> 
>>>> JSON.stringify( document )
>>>> "{"location":{}}"
>>>> 
>>>>   .
>>> 
>>> There are log limits enforced.
>> Yes, but that is not the reason for the above result.
> 
> You're right. That's just to show that there's no document loaded when he
> tested the code.

I see, but that is not a viable proof either.  I get the same with a 
document loaded because that is how JSON.stringify() works.  See below.
 
>>  This is:
>> 
>> Object.getOwnPropertyNames(document).filter(function (name) { return
>> Object.getOwnPropertyDescriptor(document, name).enumerable; })
>>| < Array [ "location" ]
>> 
>> And in Chromium:
>> 
>> JSON.stringify(document)
>>| TypeError: Converting circular structure to JSON
>> 
>> Object.getOwnPropertyNames(document).filter(function (name) { return
>> Object.getOwnPropertyDescriptor(document, name).enumerable; })
>>| Array[147]
>> 
>> The structure is “circular” in WebCore because at least “document.body”
>> and “document.body.ownerDocument” (=== document) are own, enumerable
>> properties.
>> 
>> In general, it is a Bad Idea to subject host objects to JSON
>> stringification.
> 
> I just noticed that. Why didn't JSON.stringify generate an exception?

| > Object.getOwnPropertyNames(document)
| < Array [ "location" ]

indicates that the object referred to by “document” in the Gecko DOM does 
not have own properties except “location”, which is also enumerable (and 
deprecated in favor of “window.location”).  It refers to an object that, as 
far as Object.getOwnPropertyNames() is applicable to host objects, inherits 
all of its properties:

| > Object.getOwnPropertyNames(document.location)
| Array [  ]

The next object in its prototype chain is

| > Object.getPrototypeOf(document.location)
| < XPC_WN_NoMods_NoCall_Proto_JSClass { href: Getter, hash: Getter, host: 
| Getter, hostname: Getter, pathname: Getter, port: Getter, protocol: 
| Getter, search: Getter, origin: Getter, reload: reload(), 5 more… }

which provides the expected properties.

So even though “document” is in that sense “circular” in the Gecko DOM, too, 
no object in that network of references is visited twice by Mozilla 
JavaScript’s JSON.stringify().  But the latter is a requirement for throwing 
a TypeError exception, see ES 5.1, §15.12.3, JO(value), step 1.

This is different in the WebCore DOM, even if Google V8 JavaScript that is 
used by Chromium implements the same algorithm as Mozilla JavaScript that is 
used by Firefox/Iceweasel.


A draft reference implementation of ECMAScript (current target is the 5.1 
Edition) in ECMAScript [1] is available on the ES Matrix site with the 
global “es” property.  For example, you can enter

  try { es.JSON.stringify(document); } catch (e) { e.stack }

in the console to see where and why the exception should be thrown.  I have 
also included a call tracer that you can enable with

  es.enableTrace = true;

(assigning the default “false” disables tracing again).


It is considered polite to post using one’s real name.

________
[1] <http://PointedEars.de/scripts/test/es-matrix/application/scripts/es.js>
-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

[toc] | [prev] | [next] | [standalone]

#25114

Stefan Ram wrote:

> JJ <jj4public@vfemail.net> writes:
>> Did that happen on all web pages, including blank HTML file?
> 
>   I only ever tried it in the debugger with no web page at all:
> 
> JSON.stringify( document )
> "{"location":{}}"

Works as designed, see ES 5.1 §15.12.3.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.javascript

csiph-web