Question

Django-compress is great, but it doesn’t offer any tags for compressing in-page javascript.

Are there some solutions out there? Even removing newlines (and adding “;” where needed) would be just great.

Answer 1

Okay, i’ve done this myself, using JSCompressor by Michael Palmer (http://code.activestate.com/recipes/496882/)

Here’s the code:

from django import template

def do_foldjs(parser, token):
    nodelist = parser.parse(('endfoldjs',))
    parser.delete_first_token()
    return FoldJSNode(nodelist)

class FoldJSNode(template.Node):
    def __init__(self, nodelist):
        self.nodelist = nodelist
    def render(self, context):
        output = self.nodelist.render(context)

        try:
            compressor = JSCompressor(compressionLevel=2)
            return compressor.compress(output)
        except:
            return output


import re



class JSCompressor(object):

    def __init__(self, compressionLevel=2, measureCompression=False):
        '''
        compressionLevel:
        0 - no compression, script returned unchanged. For debugging only -
            try if you suspect that compression compromises your script
        1 - Strip comments and empty lines, don't change line breaks and indentation (code remains readable)
        2 - Additionally strip insignificant whitespace (code will become quite unreadable)

        measureCompression: append a comment stating the extent of compression

            @author: Michael Palmer
            @see: http://code.activestate.com/recipes/496882/
            @see: http://webscripts.softpedia.com/developer/Michael-Palmer-8459.html
            @see: http://webscripts.softpedia.com/script/Development-Scripts-js/JavaScript-code-compression--18221.html
        '''
        self.compressionLevel = compressionLevel
        self.measureCompression = measureCompression

    # a bunch of regexes used in compression
    # first, exempt string and regex literals from compression by transient substitution

    findLiterals = re.compile(r'''
        (\'.*?(?<=[^\\])\')             |       # single-quoted strings
        (\".*?(?<=[^\\])\")             |       # double-quoted strings
        ((?<![\*\/])\/(?![\/\*]).*?(?<![\\])\/) # JS regexes, trying hard not to be tripped up by comments
        ''', re.VERBOSE)

    # literals are temporarily replaced by numbered placeholders

    literalMarker = '@_@%d@_@'                  # temporary replacement
    backSubst = re.compile('@_@(\d+)@_@')       # put the string literals back in

    mlc1 = re.compile(r'(\/\*.*?\*\/)')         # /* ... */ comments on single line
    mlc = re.compile(r'(\/\*.*?\*\/)', re.DOTALL)  # real multiline comments
    slc = re.compile('\/\/.*')                  # remove single line comments

    collapseWs = re.compile('(?<=\S)[ \t]+')    # collapse successive non-leading white space characters into one

    squeeze = re.compile('''
        \s+(?=[\}\]\)\:\&\|\=\;\,\.\+])   |     # remove whitespace preceding control characters
        (?<=[\{\[\(\:\&\|\=\;\,\.\+])\s+  |     # ... or following such
        [ \t]+(?=\W)                      |     # remove spaces or tabs preceding non-word characters
        (?<=\W)[ \t]+                           # ... or following such
        '''
        , re.VERBOSE | re.DOTALL)

    def compress(self, script):
        '''
        perform compression and return compressed script
        '''
        if self.compressionLevel == 0:
            return script

        lengthBefore = len(script)

        # first, substitute string literals by placeholders to prevent the regexes messing with them
        literals = []

        def insertMarker(mo):
            l = mo.group()
            literals.append(l)
            return self.literalMarker % (len(literals) - 1)

        script = self.findLiterals.sub(insertMarker, script)

        # now, to the literal-stripped carcass, apply some kludgy regexes for deflation...
        script = self.slc.sub('', script)       # strip single line comments
        script = self.mlc1.sub(' ', script)     # replace /* .. */ comments on single lines by space
        script = self.mlc.sub('\n', script)     # replace real multiline comments by newlines

        # remove empty lines and trailing whitespace
        script = '\n'.join([l.rstrip() for l in script.splitlines() if l.strip()])

        if self.compressionLevel == 2:              # squeeze out any dispensible whitespace
            script = self.squeeze.sub('', script)
        elif self.compressionLevel == 1:            # only collapse multiple whitespace characters
            script = self.collapseWs.sub(' ', script)

        # now back-substitute the string and regex literals
        def backsub(mo):
            return literals[int(mo.group(1))]

        script = self.backSubst.sub(backsub, script)

        if self.measureCompression:
            lengthAfter = float(len(script))
            squeezedBy = int(100*(1-lengthAfter/lengthBefore))
            script += '\n// squeezed out %s%%\n' % squeezedBy

        return script

Registration:

register = template.Library()
register.tag('foldjs', do_foldjs)