python使用正则表达式实现的javascript文件压缩代码，pythonjavascript,如下代码：'''a re

python使用正则表达式实现的javascript文件压缩代码，pythonjavascript,如下代码：'''a re

如下代码：

'''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 = '@_@%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 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)