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Steven Haryanto


Language::Expr::Compiler::JS - Compile Language::Expr expression to JavaScript


This document describes version 0.23 of module Language::Expr::Compiler::JS (in distribution Language-Expr), released on 2014-05-01.


 use Language::Expr::Compiler::JS;
 my $jsc = Language::Expr::Compiler::JS->new;
 print $jsc->js('map({$_**2}, [1, 2, 3])'); # prints: [1, 2, 3].map(function(_){ Math.pow(_, 2) })

 # map Expr function to JS function/method/property
 $jsc->func_mapping->{ceil} = 'Math.ceil';
 $jsc->func_mapping->{uc} = '.toUpperCase';
 $jsc->func_mapping->{length} = ':length';
 print $jsc->js(q{uc("party like it's ") . ceil(1998.9)}); # prints: "party like it's ".toUpperCase() + Math.ceil(1998.9)


Compiles Language::Expr expression to JavaScript code. Some notes:

  • JavaScript version

    This compiler emits JavaScript 1.8.1 code (it uses several Array methods like map() and filter() [supported since JavaScript 1.6], 'let' lexical variables [supported since JavaScript 1.7 / Firefox 2] and native JSON [supported since JavaScript 1.8.1 / Firefox 3.5]).

    Currently to test emitted JavaScript code, we use Spidermonkey 1.9.1+ JavaScript interpreter (typically located in /usr/bin/js) as the JavaScript and JE modules are still not up to par.

  • JavaScript-ness

    The emitted JS code will follow JavaScript's weak typing and coercion rules, e.g. Expr '1+"2"' will simply be translated to JavaScript '1+"2"' and will result in "12".

  • Variables by default simply use JavaScript variables.

    E.g. $a becomes a, and so on. Be careful not to make variables which are invalid in JavaScript, e.g. $.. or ${foo/bar}.

    You can customize this behaviour by subclassing rule_var() or by providing a hook_var() (see documentation in Language::Expr::Compiler::Base).

  • Functions by default simply use Javascript functions.

    Except those mentioned in func_mapping (e.g. rand() becomes Math.rand() if func_mapping->{rand} is 'Math.rand'). You can also map to JavaScript method (using '.meth' syntax) and property (using ':prop' syntax).

    You can customize this behaviour by subclassing rule_func() or by providing a hook_func() (see documentation in Language::Expr::Compiler::Base).


js($expr) => $js_code

Convert Language::Expr expression into JavaScript code. Dies if there is syntax error in expression.


Please visit the project's homepage at https://metacpan.org/release/Language-Expr.


Source repository is at https://github.com/sharyanto/perl-Language-Expr.


Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Language-Expr

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


Steven Haryanto <stevenharyanto@gmail.com>


This software is copyright (c) 2014 by Steven Haryanto.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.