python压缩javascript文件代码

通过正规表达式实现“`python
”’
a regex-based JavaScript code compression kludge
”’
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
    '''
    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 = '@[email protected]%[email protected][email protected]'                  # temporary replacement
backSubst = re.compile('@[email protected](\d+)@[email protected]')       # 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+(?=[\}\]\)\:\&amp;\|\=\;\,\.\+])   |     # remove whitespace preceding control characters
    (?<=[\{\[\(\:\&amp;\|\=\;\,\.\+])\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

if name == ‘main’:
script = ”’

/* this is a totally useless multiline comment, containing a silly "quoted string",
   surrounded by several superfluous line breaks
 */

// and this is an equally important single line comment

sth = "this string contains 'quotes', a /regex/ and a // comment yet it will survive compression";

function wurst(){           // this is a great function
    var hans = 33;
}

sthelse = 'and another useless string';

function hans(){            // another function
    var   bill   =   66;    // successive spaces will be collapsed into one;
    var bob = 77            // this line break will be preserved b/c of lacking semicolon
    var george = 88;
}
'''

for x in range(1,3):
    print '\ncompression level', x, ':\n--------------'
    c = JSCompressor(compressionLevel=x, measureCompression=True)
    cpr = c.compress(script)
    print cpr
    print 'length', len(cpr)

“`

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