slimit 0.2

SlimIt - JavaScript minifier

SlimIt is a Python library that parses JavaScript and returns AST.

At version 0.2 it includes a JavaScript parser, lexer, pretty printer and a tree visitor.

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;
}
>>>

N.B. First time you invoke parse method it will generate the lextab.py and yacctab.py LALR tables in current directory and you may see some warnings - that’s OK. Previously generated tables are cached and reused if possible. For more details visit PLY’s official site.

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)

Installation

Using pip:

$ sudo pip install slimit

Using easy_install:

$ sudo easy_install slimit

Roadmap

• Add JavaScript minification

Change History

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