python压缩javascript文件代码

概述python压缩javascript文件代码

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'''a regex-based JavaScript code compression kludge'''import reclass 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+(?=[\}\]\)\:\&\|\=\;\,\.\+])   |     # 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 scriptif __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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