Js2Py 0.27

JavaScript to Python Translator & JavaScript interpreter written in 100% pure Python.

Pure Python JavaScript Translator/Interpreter
=============================================

Translates any valid JavaScript (ECMA Script 5.1) to Python. Translation
is fully automatic. Does not have any dependencies - uses only standard
python library.

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Managed to fully automatically translate esprima to Python! - Available
Here

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Functionality
=============

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Automatically translates JavaScript to Python - Supports virtually
everything (see limitations)

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Supports importing Python libraries from JavaScript code using pyimport
statement

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Very fast JavaScript Parsing - can be used as standalone JS parser,
syntax tree is just like in esprima.js (use js2py.parse\_js)

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Provides friendly JS execution features - js2py.eval\_js for single
execution and js2py.EvalJs for continuous

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Simple Example:

::

>>> import js2py
>>> add = js2py.eval_js('function add(a, b) {return a + b}')
>>> add(1, 2) + 3
6
>>> add('1', 2, 3)
u'12'
>>> add.constructor
function Function() { [python code] }

More advanced usage example:

::

# Execute javascript in context:
>>> context = EvalJs()
>>> context.execute('var a = 10; function f(x) {return x*x};')
# Get value of variable a:
>>> context.a
10
# context.f behaves just like js function so you can supply more than 1 argument. '9'*'9' in javascript is 81.
>>> context.f('9', 0)
81
# context.f has all attributes of normal javascript object (including __proto__ )
>>> context.f.toString()
u'function f(x) { [python code] }'
>>> context.f.constructor
function Function() { [python code] }

# You can also set variables inside context:
>>> context.foo = [1,2,3] # context.foo is now Js Array object and behaves just like javascript array!
>>> context.foo.push(4)
4
>>> context.foo.to_list() # convert to python list
[1, 2, 3, 4]

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Limitations
===========

It has only 3 known limitations:

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"strict mode" is ignored

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with statement is not supported

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Indirect call to eval will is treated as direct call to eval (hence
always evals in local scope)

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Please let me know if you find any bugs - they will be fixed within 48
hours.

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Installation
============

::

pip install js2py

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Other Examples
==============

In Js2Py all JavaScript objects are a subclass of PyJs object. For
example JS Number is represented by PyJsNumber class. js2py.eval\_js and
js2py.EvalJs automatically tries to convert PyJs type to builtin python
type. So for example if you execute:

::

>>> js2py.eval_js('var a = "hello"; a')

eval\_js will return unicode type (u"hello"). However for complex types
such conversion is impossible and JsObjectWrapper is returned. See the
conversion table JsType -> PyType:

::

Boolean -> bool
String -> unicode
Number -> float (or int/long if whole number)
undefined -> None
null -> None
OTHER -> JsObjectWrapper

JsObjectWrapper supports: getitem, getattr, setitem, setattr, repr and
call. Moreover it has to\_list and to\_dict methods if you want to
convert it to builtin python type.

::

>>> js = js2py.eval_js('d = {a:1, b:2}')
>>> js
{a: 1, b: 2}
>>> type(js)
<class 'js2py.base.JsObjectWrapper'>
>>> js.a
1
>>> js['a']
1
>>> js.b = 20
>>> js
{a: 1, b: 20}
>>> js['c'] = 30
>>> js.to_dict()
{u'a': 1, 'c': 30, u'b': 20}

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Also, of course you can use Js2Py to parse (tree is the same as in
esprima.js) and translate JavaScript

Parsing:
========

::

>>> js2py.parse_js('var $ = 5')
{'body': [{'kind': 'var', 'declarations': [{'init': {'raw': None, 'type': u'Literal', 'value': 5.0}, 'type': u'VariableDeclarator', 'id': {'type': u'Identifier', 'name': u'$'}}], 'type': u'VariableDeclaration'}], 'type': u'Program'}

Translating:
============

::

>>> print js2py.translate_js('var $ = 5')
import js2py.pyjs, sys
# Redefine builtin objects... Do you have a better idea?
for m in sys.modules.keys():
if m.startswith('js2py'):
del sys.modules[m]
del js2py.pyjs
del js2py
from js2py.pyjs import *
# setting scope
var = Scope( JS_BUILTINS )
set_global_object(var)

# Code follows:
var.registers([u'$'])
var.put(u'$', Js(5.0))

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pyimport statement
==================

Finally, Js2Py also supports importing any Python code from JavaScript
using 'pyimport' statement:

::

>>> x = """pyimport urllib;
var result = urllib.urlopen('https://www.google.com/').read();
console.log(result.length)
"""
>>> js2py.eval_js(x)
18211
undefined