python spidermonkey javascript evaluation example

pysmjs.py

import os
import subprocess

def spidermonk(script, user):
        """ JavaScript wrapper

        smjs notes: not recommended for production use,
        as it contains dangerous (security-wise) debugging features.
        -- Make sure not to load unsafe javascripts!
        """

        spidermonkey = '/usr/bin/smjs' # apt-get install spidermonkey-bin
        jsheader = ''' 
                // "emulate" a DOM,
                // set up scripts environment
                function empty(){};
                window=[];
                document=[];
                document.write=empty;
                //document.write=print;

                // some custom functions
                function dec2a(dec) {
                        function convert(all,match) {
                                return String.fromCharCode(parseInt(match, 10))
                        }
                        return dec.replace(/&#(\d+);/g, convert)
                };
                author=window.author="''' + user + '''";
        '''
        jsfooter = ''' 
                // return evaluated data
                print(dec2a(mstring)+a[author].substring(i))
        '''

        # smjs
        convert = [spidermonkey,
                '-e', '%s' % jsheader,
                '-e', '%s' % script,
                '-e', '%s' % jsfooter
        ]   

        os.environ['PYTHONIOENCODING'] = 'utf-8'
        p = subprocess.Popen(
                convert,
                stdin=subprocess.PIPE,
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
        )   
        return p.communicate()[0].strip().decode('utf-8')