rJSmin - Javascript Minifier

rJSmin is a javascript minifier written in python.

The minifier is based on the semantics of jsmin.c by Douglas Crockford.

The module is a re-implementation aiming for speed, so it can be used at runtime (rather than during a preprocessing step). Usually it produces the same results as the original jsmin.c. It differs in the following ways:

  • there is no error detection: unterminated string, regex and comment literals are treated as regular javascript code and minified as such.
  • Control characters inside string and regex literals are left untouched; they are not converted to spaces (nor to \n)
  • Newline characters are not allowed inside string and regex literals, except for line continuations in string literals (ECMA-5).
  • return /regex/” is recognized correctly.
  • Line terminators after regex literals are handled more sensibly.
  • More characters are allowed before regexes
  • + +” and “- -” sequences are not collapsed to ‘++’ or ‘--
  • Newlines before ! operators are removed more sensibly
  • (Unnested) template literals are supported
  • Comments starting with an exclamation mark (‘!’) can be kept optionally
  • rJSmin does not handle streams, but only complete strings. (However, the module provides a “streamy” interface).

Since most parts of the logic are handled by the regex engine it’s way faster than the original python port of jsmin.c by Baruch Even. The speed factor varies between about 6 and 55 depending on input and python version (it gets faster the more compressed the input already is). Compared to the speed-refactored python port by Dave St.Germain the performance gain is less dramatic but still between 3 and 50 (for huge inputs).

rJSmin comes with an optional C-reimplementation of the python/regex implementation, which speeds up the minifying process even more.

Supported python versions are 2.7 and 3.4+.

Development Status

rJSmin is stable.

Documentation

The module provides a simple function (generated apidoc below), called jsmin which takes the script as a string and returns the minified script as a string.

The module additionally provides a “streamy” interface similar to the one jsmin.c provides:

$ python -mrjsmin <script >minified

This command line interface takes two options:

-b Keep bang-comments (Comments starting with an exclamation mark)
-p Force using the python implementation (not the C implementation)

API Docs

rjsmin.jsmin(script, keep_bang_comments=False)

Minify javascript based on jsmin.c by Douglas Crockford.

Instead of parsing the stream char by char, it uses a regular expression approach which minifies the whole script with one big substitution regex.

Note:

This is a hand crafted C implementation built on the regex semantics.

Parameters:
script : str

Script to minify

keep_bang_comments : bool

Keep comments starting with an exclamation mark? (/*!...*/)

Return:

Minified script

Rtype:

str

License

rJSmin is available under the terms and conditions of the “Apache License, Version 2.0.” You’ll find the detailed licensing terms in the root directory of the source distribution package or online at http://www.apache.org/licenses/LICENSE-2.0.

Download

Integrity Check

There are hashes (MD5, SHA1 and SHA256) of the download packages stored in the digests file. In order to check the integrity of the downloaded file, use a tool like md5sum (or sha1sum, sha256sum accordingly), e.g.:

$ md5sum -c rjsmin-1.1.0.digests
rjsmin-1.1.0.tar.bz2: OK
rjsmin-1.1.0.tar.gz: OK
rjsmin-1.1.0.tar.xz: OK
rjsmin-1.1.0.zip: OK

In order to check the integrity of the digest file itself, you can check the PGP signature of that file. The file is signed by André Malo, Key-ID 0x8103A37E:

$ gpg --verify rjsmin-1.1.0.digests
gpg: Signature made Wed Mar  6 18:07:52 2019 CET
gpg:                using DSA key ID 92CCEF0AA7DD46AC3A0F498BCA6939748103A37E
gpg: Good signature from "Andre Malo <nd@apache.org>"
gpg:                 aka "Andr\xe9\x20Malo <nd@perlig.de>"
gpg:                 aka "Andre Malo <ndparker@gmx.net>"

Bugs

No bugs, of course. ;-) But if you’ve found one or have an idea how to improve rJSmin, feel free to send a pull request on github or send a mail to <rjsmin-bugs@perlig.de>.

Author Information

rJSmin was written and is maintained by André Malo.

Trivia / Fun

rJSmin is a single pass substitution using a simple regular expression, which looks like this:

pattern = (
    r'([^\047"\140/\000-\040]+)|((?:(?:\047[^\047\\\r\n]*(?:\\(?:[^'
    r'\r\n]|\r?\n|\r)[^\047\\\r\n]*)*\047)|(?:"[^"\\\r\n]*(?:\\(?:[^'
    r'\r\n]|\r?\n|\r)[^"\\\r\n]*)*")|(?:\140[^\140\\]*(?:\\(?:[^\r\n'
    r']|\r?\n|\r)[^\140\\]*)*\140))[^\047"\140/\000-\040]*)|(?<=[(,='
    r':\[!&|?{};\r\n+*-])(?:[\000-\011\013\014\016-\040]|(?:/\*[^*]*'
    r'\*+(?:[^/*][^*]*\*+)*/))*(?:(?:(?://[^\r\n]*)?[\r\n])(?:[\000-'
    r'\011\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/))*)*('
    r'(?:/(?![\r\n/*])[^/\\\[\r\n]*(?:(?:\\[^\r\n]|(?:\[[^\\\]\r\n]*'
    r'(?:\\[^\r\n][^\\\]\r\n]*)*\]))[^/\\\[\r\n]*)*/))((?:[\000-\011'
    r'\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/))*(?:(?:('
    r'?://[^\r\n]*)?[\r\n])(?:[\000-\011\013\014\016-\040]|(?:/\*[^*'
    r']*\*+(?:[^/*][^*]*\*+)*/))*)+(?=[^\000-\040&)+,.:;=?\]|}-]))?|'
    r'(?<=[\000-#%-,./:-@\[-^\140{-~-]return)(?:[\000-\011\013\014\0'
    r'16-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/))*(?:((?:(?://[^\r'
    r'\n]*)?[\r\n]))(?:[\000-\011\013\014\016-\040]|(?:/\*[^*]*\*+(?'
    r':[^/*][^*]*\*+)*/))*)*((?:/(?![\r\n/*])[^/\\\[\r\n]*(?:(?:\\[^'
    r'\r\n]|(?:\[[^\\\]\r\n]*(?:\\[^\r\n][^\\\]\r\n]*)*\]))[^/\\\[\r'
    r'\n]*)*/))((?:[\000-\011\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/'
    r'*][^*]*\*+)*/))*(?:(?:(?://[^\r\n]*)?[\r\n])(?:[\000-\011\013'
    r'\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/))*)+(?=[^\000'
    r'-\040&)+,.:;=?\]|}-]))?|(?<=[^\000-!#%&(*,./:-@\[\\^{|~])(?:['
    r'\000-\011\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/)'
    r')*(?:((?:(?://[^\r\n]*)?[\r\n]))(?:[\000-\011\013\014\016-\040'
    r']|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/))*)+(?=[^\000-\040"#%-\047'
    r')*,./:-@\\-^\140|-~])|(?<=[^\000-#%-,./:-@\[-^\140{-~-])((?:['
    r'\000-\011\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/)'
    r'))+(?=[^\000-#%-,./:-@\[-^\140{-~-])|(?<=\+)((?:[\000-\011\013'
    r'\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/)))+(?=\+)|(?<'
    r'=-)((?:[\000-\011\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]'
    r'*\*+)*/)))+(?=-)|(?:[\000-\011\013\014\016-\040]|(?:/\*[^*]*\*'
    r'+(?:[^/*][^*]*\*+)*/))+|(?:(?:(?://[^\r\n]*)?[\r\n])(?:[\000-'
    r'\011\013\014\016-\040]|(?:/\*[^*]*\*+(?:[^/*][^*]*\*+)*/))*)+'
)