Gonzalo Diethelm
and 1 contributors


JavaScript::Duktape::XS - Perl XS binding for the Duktape Javascript embeddable engine


Version 0.000068


    my $vm = JavaScript::Duktape::XS->new();

    my $options = {
        gather_stats     => 1,
        save_messages    => 1,
        max_memory_bytes => 256*1024,
        max_timeout_us   => 2*1_000_000,
    my $vm = JavaScript::Duktape::XS->new($options);

    $vm->set('global_name', [1, 2, 3]);
    my $aref = $vm->get('global_name');

    $vm->set('my.object.slot', { foo => [ 4, 5 ] });
    my $href = $vm->get('my.object.slot');

    if ($vm->exists('my.object.slot')) { ... }

    my $typeof = $vm->typeof('my.object.slot');

    my $ok = $vm->instanceof('my.car.object', 'Car');

    # When function_name is called from JS, the arguments passed in
    # will be converted to Perl values; likewise, the value returned
    # from the Perl function will be converted to JS values.
    $vm->set('function_name', sub { my @args = @_; return \@args; });
    my $returned = $vm->eval('function_name(my.object.slot)');


    my $stats_href = $vm->get_stats();

    my $msgs_href = $vm->get_msgs();

    my $globals = $vm->global_objects();

    my $context = $vm->parse_js_stacktrace($stacktrace_lines, 2);

    my $rounds = $vm->run_gc();

    $vm->set('perl_module_resolve', \&module_resolve);
    $vm->set('perl_module_load',    \&module_load);
    $vm->eval('var badger = require("badger");');


This module provides an XS wrapper to call Duktape from Perl.

The wrapper is used in an OO way: you create an instance of JavaScript::Duktape::XS and then invoke functions on it.



Create a new instance of JavaScript::Duktape::XS. You can give an optional hashref with a set of desired options; they can be:


The XS object will gather statistics about elapsed time and memory usage for several of its operations. You can then retrieve the stats by calling get_stats.


Any message printed to the JavaScript console will instead be saved in a hashref, where each key represents a "target" for the message (for example, stdout or stderr). You can then retrieve the messages by calling get_msgs.


Limit the memory dynamically allocated to this many bytes. If this option is not used, there is no limit in place.


Limit the execution runtime of any single JavaScript call to this many microseconds. If this option is not used, there is no limit in place.


Give a value to a given JavaScript variable or object slot.

The Perl value is converted into an equivalent JavaScript value, so you can freely pass nested structures (hashes of arrays of hashes) and they will be handled correctly.

You can also pass a Perl coderef as a value, in which case the named JavaScript variable / object slot becomes a function which, when executed, will end up calling the Perl coderef. Any values passed from JavaScript into the Perl coderef will be properly converted into equivalent Perl values; likewise, any values returned from the Perl coderef back to JavaScript will be also converted into equivalent JavaScript values.


Get the value stored in a JavaScript variable or object slot.

The JavaScript value is converted into an equivalent Perl value, so you can freely pass nested structures (hashes of arrays of hashes) and they will be handled correctly.


Checks to see if there is a value stored in a JavaScript variable or object slot. Returns a boolean and avoids all JavaScript to Perl value conversions.


Returns a string with the JavaScript type of a given variable. Possible returned values are undefined, null, boolean, number, string, array, object, symbol, function, pointer, c_function, lightfunc, thread, buffer.

This method returns null for null values, which fixes the long-standing JavaScript bug of returning object for null values.


Returns a true value when the variable given by the first parameter is an instance of the class given by the second parameter.


Run a piece of JavaScript code, given as a string, and return the results.

For now the XS object will both compile and run the JavaScript code when this method is invoked; in the future this might be split into separate functions.

Any returned values will be treated in the same way as a call to get.


Run a JavaScript function inside an event loop, and wait until all timers have been dispatched. The argument is the function name.

If the function name is 'X', this is equivalent to running the following piece of JavaScript code:

    setTimeout(function() { X(); }, 0);


Return a hashref with the statistics gathered as a result of creating the XS object with option gather_stats set to true.


Reset the accumulated statistics, as if the XS object had just been created.


Return a hashref with the messages collected as a result of creating the XS object with option save_messages set to true.


Reset the accumulated messages, as if the XS object had just been created.


Get an arrayref with the names of all global objects known to JavaScript.


Parse a JavaScript stacktrace (usually returned via get_msgs) and obtain structured information from it. For each of the number of frames requested (default to 1), it gets the error message, the file name and line number where the error happened, and an array of lines surrounding the actual error message.

The optional third parameter is an arrayref containing names of files that should be treated as top priority, meaning any errors pointing to those files will appear first in the returned stacktrace information.


Run at least one round of the JavaScript garbage collector, and return the number of rounds that were effectively run.

The documentation recommends to run two rounds, so that's what we always do.


There is support for managing JavaScript modules in the style of node.js. In order to do this, you need to set two Perl callbacks:

    $vm->set('perl_module_resolve', \&module_resolve);
    $vm->set('perl_module_load',    \&module_load);

Please see https://github.com/svaarala/duktape/tree/master/extras/module-node for more details.



Copyright (C) Gonzalo Diethelm.

This library is free software; you can redistribute it and/or modify it under the terms of the MIT license.


  • Gonzalo Diethelm gonzus AT cpan DOT org