js瘦身有道--选好合适的减肥药
现在的系统为了得到更好的用户体验，都加入了ajax的特效，只要用到了ajax的代码，就会引来一大堆js代码，这些代码其实也挺占用带宽的，为了使网页加载得更快，决定在项目中才用网上流行的js压缩器来压缩代码。压缩后的代码基本可以抽掉40%左右的脂肪。
找到几个压缩器，发现很多压缩器压缩后的js代码都出现这样或那样的问题
ESC 1.14 http://www.saltstorm.net/depo/esc/?pod=js 压缩后有些中文会出现问号（我的js代码是用utf-8格式）
jsmin http://www.crockford.com/javascript/jsmin.html 压缩后有些中文会出现问号
dean edwards的packer http://dean.edwards.name/packer/ 压缩后的js代码会出现部分分号或大括号丢失，导致语法错误
最后找到了yuicompressor-2.3.4 http://developer.yahoo.com/yui/compressor/ 感觉很好用，压缩后无损代码，而且连css也可以压缩，压缩的时候很多参数可以设置，可以制定js代码的编码格式等，java运行，本人写了一个bat批处理遍历制定文件夹里面的所有js和css文件进行压缩。
项目中用到网上流行的ext2 js库，所以项目中有很多js代码，于是写的bat遍历文件压缩代码
(dir
%
1
/
aa
/
b
/
s
|
findstr
/
e
/
c:
"
js
"
)
>
tmp.txt
for / f %% i in (tmp.txt) do java - jar yuicompressor - 2.3 . 4 .jar -- type js -- charset utf - 8 - o %% i.tmp %% i & copy %% i " .tmp " %% i & del %% i " .tmp "
(dir % 1 / aa / b / s | findstr / e / c: " css " ) > tmp.txt
for / f %% i in (tmp.txt) do java - jar yuicompressor - 2.3 . 4 .jar -- type css -- charset utf - 8 - o %% i.tmp %% i & copy %% i " .tmp " %% i & del %% i " .tmp "
for / f %% i in (tmp.txt) do java - jar yuicompressor - 2.3 . 4 .jar -- type js -- charset utf - 8 - o %% i.tmp %% i & copy %% i " .tmp " %% i & del %% i " .tmp "
(dir % 1 / aa / b / s | findstr / e / c: " css " ) > tmp.txt
for / f %% i in (tmp.txt) do java - jar yuicompressor - 2.3 . 4 .jar -- type css -- charset utf - 8 - o %% i.tmp %% i & copy %% i " .tmp " %% i & del %% i " .tmp "
保存为 jscompressor.bat 运行的时候在输入 jscompressor <path> (<path>是我们指定的路径) 就可以批量进行压缩，压缩后替换压缩前的代码。
下面是一些参数的说明。
==============================================================================
YUI Compressor
==============================================================================
NAME
YUI Compressor - The Yahoo ! JavaScript and CSS Compressor
SYNOPSIS
Usage: java - jar yuicompressor - x.y.z.jar [options] [input file]
Global Options
- h, -- help Displays this information
-- type < js | css > Specifies the type of the input file
-- charset < charset > Read the input file using < charset >
-- line - break < column > Insert a line break after the specified column number
- v, -- verbose Display informational messages and warnings
- o < file > Place the output into < file > . Defaults to stdout.
JavaScript Options
-- nomunge Minify only, do not obfuscate
-- preserve - semi Preserve all semicolons
-- disable - optimizations Disable all micro optimizations
DESCRIPTION
The YUI Compressor is a JavaScript compressor which, in addition to removing
comments and white - spaces, obfuscates local variables using the smallest
possible variable name. This obfuscation is safe, even when using constructs
such as ' eval ' or ' with ' (although the compression is not optimal is those
cases) Compared to jsmin, the average savings is around 20 % .
The YUI Compressor is also able to safely compress CSS files. The decision
on which compressor is being used is made on the file extension (js or css)
GLOBAL OPTIONS
- h, -- help
Prints help on how to use the YUI Compressor
-- line - break
Some source control tools don ' t like files containing lines longer than,
say 8000 characters. The linebreak option is used in that case to split
long lines after a specific column. It can also be used to make the code
more readable, easier to debug (especially with the MS Script Debugger)
Specify 0 to get a line break after each semi - colon in JavaScript, and
after each rule in CSS.
-- type js | css
The type of compressor (JavaScript or CSS) is chosen based on the
extension of the input file name (.js or .css) This option is required
if no input file has been specified. Otherwise, this option is only
required if the input file extension is neither ' js ' nor ' css ' .
-- charset character - set
If a supported character set is specified, the YUI Compressor will use it
to read the input file. Otherwise, it will assume that the platform ' s
default character set is being used. The output file is encoded using
the same character set.
- o outfile
Place output in file outfile. If not specified, the YUI Compressor will
default to the standard output, which you can redirect to a file.
- v, -- verbose
Display informational messages and warnings.
JAVASCRIPT ONLY OPTIONS
-- nomunge
Minify only. Do not obfuscate local symbols.
-- preserve - semi
Preserve unnecessary semicolons (such as right before a ' } ' ) This option
is useful when compressed code has to be run through JSLint (which is the
case of YUI for example)
-- disable - optimizations
Disable all the built - in micro optimizations.
YUI Compressor
==============================================================================
NAME
YUI Compressor - The Yahoo ! JavaScript and CSS Compressor
SYNOPSIS
Usage: java - jar yuicompressor - x.y.z.jar [options] [input file]
Global Options
- h, -- help Displays this information
-- type < js | css > Specifies the type of the input file
-- charset < charset > Read the input file using < charset >
-- line - break < column > Insert a line break after the specified column number
- v, -- verbose Display informational messages and warnings
- o < file > Place the output into < file > . Defaults to stdout.
JavaScript Options
-- nomunge Minify only, do not obfuscate
-- preserve - semi Preserve all semicolons
-- disable - optimizations Disable all micro optimizations
DESCRIPTION
The YUI Compressor is a JavaScript compressor which, in addition to removing
comments and white - spaces, obfuscates local variables using the smallest
possible variable name. This obfuscation is safe, even when using constructs
such as ' eval ' or ' with ' (although the compression is not optimal is those
cases) Compared to jsmin, the average savings is around 20 % .
The YUI Compressor is also able to safely compress CSS files. The decision
on which compressor is being used is made on the file extension (js or css)
GLOBAL OPTIONS
- h, -- help
Prints help on how to use the YUI Compressor
-- line - break
Some source control tools don ' t like files containing lines longer than,
say 8000 characters. The linebreak option is used in that case to split
long lines after a specific column. It can also be used to make the code
more readable, easier to debug (especially with the MS Script Debugger)
Specify 0 to get a line break after each semi - colon in JavaScript, and
after each rule in CSS.
-- type js | css
The type of compressor (JavaScript or CSS) is chosen based on the
extension of the input file name (.js or .css) This option is required
if no input file has been specified. Otherwise, this option is only
required if the input file extension is neither ' js ' nor ' css ' .
-- charset character - set
If a supported character set is specified, the YUI Compressor will use it
to read the input file. Otherwise, it will assume that the platform ' s
default character set is being used. The output file is encoded using
the same character set.
- o outfile
Place output in file outfile. If not specified, the YUI Compressor will
default to the standard output, which you can redirect to a file.
- v, -- verbose
Display informational messages and warnings.
JAVASCRIPT ONLY OPTIONS
-- nomunge
Minify only. Do not obfuscate local symbols.
-- preserve - semi
Preserve unnecessary semicolons (such as right before a ' } ' ) This option
is useful when compressed code has to be run through JSLint (which is the
case of YUI for example)
-- disable - optimizations
Disable all the built - in micro optimizations.