in reply to Accessing javascript variable from perl

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

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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

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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>

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    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",

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    LanX proposal fails also: 
    my ($val, $type) = $js->eval_in_page('(function() {return JSON.stringi
+fy(leg);})()');
print "val: $val, type: $type\n";

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    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.

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    Update:

    The content seems strange to me, should the js code not be include in script tag ?

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      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

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        With the file jello.jshello.js 
        var leg = {
aa: "Hello from javascript"
}

function to_json() {
   return JSON.stringify(leg);
}

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        And the file perl.pl 
        use strict;
use warnings;
use WWW::Mechanize::PhantomJS;
my $js = WWW::Mechanize::PhantomJS->new(launch_exe=> 'C:/prog/phantomj
+s/bin/phantomjs.exe');
$js->get_local("hello.js");
#$js->update_html('<script src="hello.js" type="text/javascript"></scr
+ipt>');
#print $js->content;
#my ($val, $type) = $js->eval_in_page('JSON.stringify(window.leg);');
my ($val, $type) = $js->eval_in_page('to_json()');
print "val: $val, type: $type\n";

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        I can't have any meaningfull result from calling eval_in_page either on the leg var directly or via the function.

        Can you show me how to have this working ?

        Thanks

        Update without phantomjs 
        use strict;
use warnings;
use Log::Log4perl qw(:easy);
Log::Log4perl->easy_init($ERROR);
use WWW::Mechanize::Chrome;
my $js = WWW::Mechanize::Chrome->new(report_js_errors=>1);
$js->get_local("hello.js");
#$js->update_html('<script src="hello.js" type="text/javascript"></scr
+ipt>');
#print $js->content;
#my ($val, $type) = $js->eval_in_page('JSON.stringify(window.leg);');
my ($val, $type) = $js->eval_in_page('to_json()');
print "val: $val, type: $type\n";

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        This gives undef for $val whatever I'm calling: the to_json() function or JSON.stringify directly.

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