Accessing javascript variable from perl

frazap has asked for the wisdom of the Perl Monks concerning the following question:

I have a javascript file that contains a bunch of variables.

var leg = {
aa: "a label",
ab: "another label",
....
};
var map = {
aa : ["R1"],
ab : ["AA1"],
ac : ["AA1", "AA2"],
....
};
var monorows = [
["R6", "c", "1", "CB16", "CB15" ... codes that are listed in map],
...
];
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I want to check that these variables are coherent, eg all codes in map are also in monorows, etc. In a first step, I copied the javascript variables in a perl script, changed the syntax to have json data instead of javascript syntax and could run my checks:

use JSON;
use Data::Dump "dd";
my $leg_str =<<'END';
{
"aa": "label1",
"ab": "label2",
...
"er": "last label"
}
END
my $leg = decode_json($leg_str);
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Now, I would like to automatize the import step. I tried this:

use WWW::Mechanize::PhantomJS;
my $js = WWW::Mechanize::PhantomJS->new();
    $js->get_local("my_js_file.js");
#print $js->content; I get the content ok here.
my ($val, $type) = $js->eval_in_page('function(){JSON.stringify(leg);}
+');
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But this just return in $val the function is have sent... What am I missing ? is there a way to have this working ?

Thanks

frazap

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Re: Accessing javascript variable from perl by Corion (Patriarch) on Jun 14, 2019 at 12:26 UTC
You need to at least `return` the value you want in Javascript, and I don't thzink you need the `function` at all: `$js->eval_in_page(<<'JS'); return JSON.stringify(leg); JS` [download]	[reply] [d/l] [select]
Re^2: Accessing javascript variable from perl by LanX (Saint) on Jun 14, 2019 at 12:34 UTC
> `return JSON.stringify(leg);` Does one really need return in an eval? Looked into the documentation and it doesn't seem so. But of course you know the author of WWW::Mechanize::PhantomJS better than me... ;) Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}	[reply] [d/l]
Re^2: Accessing javascript variable from perl by frazap (Monk) on Jun 14, 2019 at 13:42 UTC
The content calls says: `<html><head></head><body><pre style="word-wrap: break-word; white-spac +e: pre-wrap;"> //list of the entries in the headings drop box //the keys give the corresponding elements in the rows var leg = { aa: " ... ", ... }; </pre></body></html>` [download] The return statement gives an error if not included in a `'function () {}'` `Error while executing command: executeScript: An unknown server-side e +rror occurred while processing the command.: {"errorMessage":"Return +statements are only valid inside functions",` [download] LanX proposal fails also: `my ($val, $type) = $js->eval_in_page('(function() {return JSON.stringi +fy(leg);})()'); print "val: $val, type: $type\n";` [download] Gives the error Error while executing command: executeScript: An unknown server-side e +rror occurred while processing the command.: {"errorMessage":"Can't f +ind variable: leg","request":{"headers":{"Accept":"application/json", +"Connection":"TE, close","Content-Length":"74","Content-Type":"applic +ation/json; charset=utf-8","Host":"127.0.0.1:8910","TE":"deflate,gzip +;q=0.3","User-Agent":"libwww-perl/6.15"},"httpVersion":"1.1","method" +:"POST","post":"{\"args\":[],\"script\":\"return (function() {return +JSON.stringify(leg);})()\"}","url":"/execute","urlParsed":{"anchor":" +","query":"","file":"execute","directory":"/","path":"/execute","rela +tive":"/execute","port":"","host":"","password":"","user":"","userInf +o":"","authority":"","protocol":"","source":"/execute","queryKey":{}, +"chunks":["execute"]},"urlOriginal":"/session/95efd1d0-8ea9-11e9-b043 +-85beee600173/execute"}} at C:/strawberry/perl/site/lib/Selenium/Remo +te/Driver.pm line 389. [download] Update: The content seems strange to me, should the js code not be include in script tag ?	[reply] [d/l] [select]
Re^3: Accessing javascript variable from perl by LanX (Saint) on Jun 14, 2019 at 14:51 UTC
The errorMessages are explicitly given! `"Return statements are only valid inside functions"` I explained this already `"Can't find variable: leg"` so my proposal doesnt fail it's your JS Code. Either you can't access the namespace of `leg` or you misspelled it. Though you may want to try `window.leg` or play around inside your browser's JS console (normally type F12 to get there) HINT: `var` denotes a lexical var inside a function°, it only becomes global* if used outside. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice} updates °) mostly like `my` in Perl except for the hoisting effect *) in this case it behaves mostly like `our` in Perl	[reply] [d/l] [select]
Re^4: Accessing javascript variable from perl by frazap (Monk) on Jun 18, 2019 at 07:18 UTC
Re^5: Accessing javascript variable from perl by LanX (Saint) on Jun 18, 2019 at 08:15 UTC
Re^5: Accessing javascript variable from perl by LanX (Saint) on Jun 18, 2019 at 11:15 UTC
Some notes below your chosen depth have not been shown here
Re: Accessing javascript variable from perl by LanX (Saint) on Jun 14, 2019 at 12:28 UTC
That's more a JS question I think you are only declaring the function without calling it. `'function(){JSON.stringify(leg);}'` So better try `'(function(){return JSON.stringify(leg);})()` Or just skip the anonymous function `'JSON.stringify(leg)'` Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice} Update: And Corion is of course right, you need - contrary to Perl - an explicit return in side JS functions Update added `return` to code	[reply] [d/l] [select]

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