::

  _____ _      _____ __  __ _____ _______
 / ____| |    |_   _|  \/  |_   _|__   __|
| (___ | |      | | | \  / | | |    | |
 \___ \| |      | | | |\/| | | |    | |
 ____) | |____ _| |_| |  | |_| |_   | |
|_____/|______|_____|_|  |_|_____|  |_|

Welcome to SlimIt

SlimIt is a JavaScript minifier written in Python.
It compiles JavaScript into more compact code so that it downloads
and runs faster.

SlimIt also provides a library that includes a JavaScript parser,
lexer, pretty printer and a tree visitor.

http://slimit.readthedocs.org/ <http://slimit.readthedocs.org/>_

Installation

::

$ [sudo] pip install slimit

Or the bleeding edge version from the git master branch:

::

$ [sudo] pip install git+https://github.com/rspivak/slimit.git#egg=slimit

There is also an official DEB package available at
http://packages.debian.org/sid/slimit <http://packages.debian.org/sid/slimit>_

Let's minify some code

From the command line:

::

$ slimit -h
Usage: slimit [options] [input file]

If no input file is provided STDIN is used by default.
Minified JavaScript code is printed to STDOUT.

Options:
  -h, --help            show this help message and exit
  -m, --mangle          mangle names
  -t, --mangle-toplevel
                        mangle top level scope (defaults to False)

$ cat test.js
var foo = function( obj ) {
        for ( var name in obj ) {
                return false;
        }
        return true;
};
$
$ slimit --mangle < test.js
var foo=function(a){for(var b in a)return false;return true;};

Or using library API:

from slimit import minify
text = """
... var foo = function( obj ) {
... for ( var name in obj ) {
... return false;
... }
... return true;
... };
... """

print minify(text, mangle=True, mangle_toplevel=True)
var a=function(a){for(var b in a)return false;return true;};

Iterate over, modify a JavaScript AST and pretty print it

from slimit.parser import Parser
from slimit.visitors import nodevisitor
from slimit import ast

parser = Parser()
tree = parser.parse('for(var i=0; i<10; i++) {var x=5+i;}')
for node in nodevisitor.visit(tree):
... if isinstance(node, ast.Identifier) and node.value == 'i':
... node.value = 'hello'
...

print tree.to_ecma() # print awesome javascript :)
for (var hello = 0; hello < 10; hello++) {
var x = 5 + hello;
}

Writing custom node visitor

from slimit.parser import Parser
from slimit.visitors.nodevisitor import ASTVisitor

text = """
... var x = {
... "key1": "value1",
... "key2": "value2"
... };
... """

class MyVisitor(ASTVisitor):
... def visit_Object(self, node):
... """Visit object literal."""
... for prop in node:
... left, right = prop.left, prop.right
... print 'Property key=%s, value=%s' % (left.value, right.value)
... # visit all children in turn
... self.visit(prop)
...

parser = Parser()
tree = parser.parse(text)
visitor = MyVisitor()
visitor.visit(tree)
Property key="key1", value="value1"
Property key="key2", value="value2"

Using lexer in your project

from slimit.lexer import Lexer
lexer = Lexer()
lexer.input('a = 1;')
for token in lexer:
... print token
...
LexToken(ID,'a',1,0)
LexToken(EQ,'=',1,2)
LexToken(NUMBER,'1',1,4)
LexToken(SEMI,';',1,5)

You can get one token at a time using token method:

lexer.input('a = 1;')
while True:
... token = lexer.token()
... if not token:
... break
... print token
...
LexToken(ID,'a',1,0)
LexToken(EQ,'=',1,2)
LexToken(NUMBER,'1',1,4)
LexToken(SEMI,';',1,5)

LexToken instance has different attributes:

lexer.input('a = 1;')
token = lexer.token()
token.type, token.value, token.lineno, token.lexpos
('ID', 'a', 1, 0)

Benchmarks

SAM - JQuery size after minification in bytes (the smaller number the better)

+-------------------------------+------------+------------+------------+
| Original jQuery 1.6.1 (bytes) | SlimIt SAM | rJSmin SAM | jsmin SAM |
+===============================+============+============+============+
| 234,995 | 94,290 | 134,215 | 134,819 |
+-------------------------------+------------+------------+------------+

Roadmap

when doing name mangling handle cases with 'eval' and 'with'
foo["bar"] ==> foo.bar
consecutive declarations: var a = 10; var b = 20; ==> var a=10,b=20;
reduce simple constant expressions if the result takes less space:
1 +2 * 3 ==> 7
IF statement optimizations
1. if (foo) bar(); else baz(); ==> foo?bar():baz();
2. if (!foo) bar(); else baz(); ==> foo?baz():bar();
3. if (foo) bar(); ==> foo&&bar();
4. if (!foo) bar(); ==> foo||bar();
5. if (foo) return bar(); else return baz(); ==> return foo?bar():baz();
6. if (foo) return bar(); else something(); ==> {if(foo)return bar();something()}
remove unreachable code that follows a return, throw, break or
continue statement, except function/variable declarations
parsing speed improvements

Acknowledgments

The lexer and parser are built with PLY <http://www.dabeaz.com/ply/>_
Several test cases and regexes from jslex <https://bitbucket.org/ned/jslex>_
Some visitor ideas - pycparser <http://code.google.com/p/pycparser/>_
Many grammar rules are taken from rkelly <https://github.com/tenderlove/rkelly>_
Name mangling and different optimization ideas - UglifyJS <https://github.com/mishoo/UglifyJS>_
ASI implementation was inspired by pyjsparser <http://bitbucket.org/mvantellingen/pyjsparser>_

License

The MIT License (MIT)

Change History

0.8.1 (2013-03-26)

Bug fix: https://github.com/rspivak/slimit/pull/45
Fix syntax error in the output of for statement with some form of expressions

0.8.0 (2013-03-23)

Python 3.x support
Bug fix: https://github.com/rspivak/slimit/issues/42
slimit removes parentheses from ternary expression, causes syntax error in jQuery
Bug fix: https://github.com/rspivak/slimit/issues/37
simple identifier in FOR init
Bug fix: https://github.com/rspivak/slimit/issues/36
using $ for mangled function names conflicts with jQuery

0.7.4 (2012-06-5)

Bug fix: https://github.com/rspivak/slimit/issues/34
'class' is reserved keyword now

0.7.3 (2012-05-21)

Bug fix (unary op in FOR init): https://github.com/rspivak/slimit/pull/33

0.7.2 (2012-05-17)

Added support for get/set properties:
https://github.com/rspivak/slimit/issues/32

0.7.1 (2012-05-10)

Function call support in FOR init section:
https://github.com/rspivak/slimit/pull/31

0.7 (2012-04-16)

Multiline string support: https://github.com/rspivak/slimit/issues/24

0.6.2 (2012-04-07)

Bug fix: https://github.com/rspivak/slimit/issues/29
Bug fix: https://github.com/rspivak/slimit/issues/28

0.6.1 (2012-03-15)

Added command-line option -t/--mangle-toplevel to turn on
global scope name mangling. As of this version it's off by
default: https://github.com/rspivak/slimit/issues/27
Removed dependency on a 'distribute' package
Bug fix: https://github.com/rspivak/slimit/issues/26
Bug fix: https://github.com/rspivak/slimit/issues/25

0.6 (2012-02-04)

Added optimization: foo["bar"] ==> foo.bar
Added base class for custom AST node visitors
Documentation updates
Bug fix: https://github.com/rspivak/slimit/issues/22
Bug fix: https://github.com/rspivak/slimit/issues/21

0.5.5 (2011-10-05)

Bugfix: https://github.com/rspivak/slimit/issues/7

0.5.4 (2011-10-01)

Bugfix: https://github.com/rspivak/slimit/issues/6
Division with "this" fails

0.5.3 (2011-06-29)

Bugfix: https://github.com/rspivak/slimit/issues/5

0.5.2 (2011-06-14)

Bugfix: https://github.com/rspivak/slimit/issues/4
Bugfix: https://github.com/rspivak/slimit/issues/3

0.5.1 (2011-06-06)

Bugfix: https://github.com/rspivak/slimit/issues/2

0.5 (2011-06-06)

Added name mangling

0.4 (2011-05-12)

Minify more by removing block braces { }
More tests

0.3.2 (2011-05-09)

More hacks to use pre-generated lex and yacc tables when called from
the command line

0.3.1 (2011-05-09)

Use pre-generated lex and yacc tables when called from the command line

0.3 (2011-05-09)

Added minifier

0.2 (2011-05-07)

Added a JavaScript parser
Added pretty printer
Added node visitor

0.1 (2011-05-02)

Initial public version. It contains only a JavaScript lexer

Package profile

slimit

Dependencies

Details

Package description