_____ _ _____ __ __ _____ _______
/ ____| | / __ __|
(___ | | | | | / | | | | | ___ | | | | | | | | | | ____) | | | |_______| _____|
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.
$ [sudo] pip install slimit
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
$ cat test.js
var a = function( obj ) {
for ( var name in obj ) {
return false;
}
return true;
};
$
$ slimit --mangle < test.js
var a=function(a){for(var b in a)return false;return true;};
Or using library API:
>>> from slimit import minify >>> text = """ ... var a = function( obj ) { ... for ( var name in obj ) { ... return false; ... } ... return true; ... }; ... """ >>> print minify(text, mangle=True) var a=function(a){for(var b in a)return false;return true;};
>>> 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; } >>>
>>> 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"
>>> 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)
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 |
- 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
- if (foo) bar(); else baz(); ==> foo?bar():baz();
- if (!foo) bar(); else baz(); ==> foo?baz():bar();
- if (foo) bar(); ==> foo&&bar();
- if (!foo) bar(); ==> foo||bar();
- if (foo) return bar(); else return baz(); ==> return foo?bar():baz();
- 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