年末将至，很多闲适的时间，于是刷刷微博，接触各种纷杂的信息——美其名曰“学习”。运气不错，遇到了一个新名词，uglifyjs. 据说是用来压缩JS文件的，据说还能优化JS,据说是基于node的，还据说比Google Closure Compiler更带感，哦？激起了我的好奇心。百之谷之，哟，相关的介绍还不少。然后折腾了个把小时，基本上知道了是个怎么回事。
我觉得吧，还是有些用的，即使是不是从事node开发的人，抽个小空，share之，于是就有了本文。人总有浮躁的时候，我也不例外，uglifyjs内部深入的运作是如何的，唉，我是有气无力，不想去折腾，所以，本文更多是停留在应用层面。不过嘛，这样反而受众面广一些。毕竟喜欢看《泰囧》的人要比《一代宗师》的多。
凡事提及node应用，无非免不了类似下面的流程：
前两个网上太多示意了，我之前也讲过，sorry, 我很懒。
uglifyjs安装如下code:
npm install uglify-js -g
一个回车，于是啪啪啪，就有下图所示的东东：
于是，下面就可以压缩JS了。
uglifyjs压缩有很多的参数，详见其github托管项目。其中有一些可选参数，如下部分截图：
什么美化压缩，空格多长，变量名是否变成短名字等……您有兴趣可以自己去看看，如果今天不是星期五，如果不是要赶回去买菜，我就会翻译下的——诸位，请原谅我吧，阿门！
下面演示如何使用uglifyjs压缩JS.
我的桌面上有个名叫formini的文件夹，我会把要压缩的文件放在其中，然后再压缩。现在，我从内部拷贝了一个名叫inet.js的JS文件到这个文件夹中，然后：
uglifyjs inet.js -o inet-min.js
-m可选参数：
uglifyjs inet.js -m -o inet.min.js
如下截图：
噢啦，现在就是看结果了，见下截图：
90K的是没有运行-m参数的，70K(69.4)的是运行的。-m参数所以就是把变量名变成a, b, c, d, ...
从实际应用角度讲，上线的JS显然要压缩变量，减小一定的文件尺寸。
跟YUICompressor相比，大小只小了0.6K, 不过网上反映uglifyjs相比YUI压缩很明显，我这里的大小仅优化了0.6÷174=0.345%，这只能说明我写的代码还算比较优化，哈哈（突然想起了老婆的话，不要得瑟，深呼吸……深呼吸……）！
我们不可能每次都打开cmd去键入压缩执行代码，容易写错不说（如上面那个结果图），还耗时，想想都会让人疯掉。懒人有懒法，花了点功夫，折腾了一个批处理文件，以后，想要压缩JS，只要双击运行这个.bat文件就可以了！完整代码如下：
@echo off
:: 设置压缩JS文件的根目录，脚本会自动按树层次查找和压缩所有的JS
SET JSFOLDER=C:\Users\Administrator\Desktop\formini
echo 正在查找JS文件
chdir /d %JSFOLDER%
for /r . %%a in (*.js) do (
@echo 正在压缩 %%~a ...
uglifyjs %%~fa -m -o %%~fa
)
echo 完成!
pause & exit
新建一个txt文档，任意命名，将上面的代码粘贴进去，修改JSFOLDER后面的文件夹目录为你自己的，然后把.txt后缀改成.bat就可以啦！然后双击就可以批量使用uglifyjs压缩JS文件啦！
对于自己来讲，本文内容算作备忘。目前而言，我还是uglifyjs不能压缩CSS文件。不过嘛，了解下总会有帮助的。行文匆忙，文中要是有表述不准确的地方欢迎指正。
另外一篇文章介绍
做Web前端开发，总是要考虑页面的打开速度，如果文件数量越少、文件长度越小，就可以直接的提升网页的访问速度。
但在开发的时候，为了保证代码的可读性，我们写的程序文件会很多而且很大，这样就与部署的要求发生背离，通过UglifyJS2这个工具，我们可以在开发完成时，对代码文件进行 合并、混淆、压缩 等的操作，达到最优的访问性能。
开始UglifyJS2介绍之前，我们先要说一下UglifyJS。 UglifyJS 是UglifyJS2的前身，是一个Javascript开发的通用的语法分析、代码压缩、代码优化的一个工具包。UglifyJS是基于Nodejs环境开发，支持CommonJS模块系统的任意的Javascript平台。
UglifyJS的实现主要分为2部分：
UglifyJS2 是作者对UglifyJS的重写，是完全的重写，而不仅仅是升级。从UglifyJS2官司方网页介绍看，UglifyJS2把整个的JS压缩过程，做了更进一步的细化。
上述所有的功能代码API是 在6500行的左右，比其他的相同功能的开发包都要小。作者还提供了一个在线版本UglifyJS2的JS压缩工具， http://lisperator.net/uglifyjs/，大家可以测试一下。
系统环境：
UglifyJS2的安装非常简单，和Nodejs的其他包一样，全局安装使用如下命令。
npm install uglify-js -g也可以通过github下载源代码安装。
git clone git://github.com/mishoo/UglifyJS2.git
cd UglifyJS2
我们在使用UglifyJS2的时候主要有2种方式，一种是通过命令行操作，对指定的JS文件进行压缩；另一种是通过程序的API调用，对文件或内存中的JS代码进行压缩。下面我将分两种情况进行介绍。
在全局安装好UglifyJS2以后，我们就可以使用UglifyJS2的命令了。
打印uglifyjs命令行的帮助信息，会打出很长一段说明。
D:\workspace\javascript\nodejs-uglifyJS2>uglifyjs -h
D:\toolkit\nodejs\\node.exe D:\toolkit\nodejs\node_modules\uglify-js\bin\uglifyjs input1.js [input2.js ...] [options]
Use a single dash to read input from the standard input.
NOTE: by default there is no mangling/compression.
Without [options] it will simply parse input files and dump the AST
with whitespace and comments discarded. To achieve compression and
mangling you need to use `-c` and `-m`.
Options:
--source-map Specify an output file where to generate source
map. [string]
--source-map-root The path to the original source to be included
in the source map. [string]
--source-map-url The path to the source map to be added in //#
sourceMappingURL. Defaults to the value passed
with --source-map. [string]
--source-map-include-sources Pass this flag if you want to include the
content of source files in the source map as
sourcesContent property. [boolean]
--in-source-map Input source map, useful if you‘re compressing
JS that was generated from some other original
code.
--screw-ie8 Pass this flag if you don‘t care about full
compliance with Internet Explorer 6-8 quirks
(by default UglifyJS will try to be IE-proof).
[boolean]
--expr Parse a single expression, rather than a
program (for parsing JSON) [boolean]
-p, --prefix Skip prefix for original filenames that appear
in source maps. For example -p 3 will drop 3
directories from file names and ensure they are
relative paths. You can also specify -p
relative, which will make UglifyJS figure out
itself the relative paths between original
sources, the source map and the output file.
[string]
-o, --output Output file (default STDOUT).
-b, --beautify Beautify output/specify output options.
[string]
-m, --mangle Mangle names/pass mangler options. [string]
-r, --reserved Reserved names to exclude from mangling.
-c, --compress Enable compressor/pass compressor options. Pass
options like -c
hoist_vars=false,if_return=false. Use -c with
no argument to use the default compression
options. [string]
-d, --define Global definitions [string]
-e, --enclose Embed everything in a big function, with a
configurable parameter/argument list. [string]
--comments Preserve copyright comments in the output. By
default this works like Google Closure, keeping
JSDoc-style comments that contain "@license" or
"@preserve". You can optionally pass one of the
following arguments to this flag:
- "all" to keep all comments
- a valid JS regexp (needs to start with a
slash) to keep only comments that match.
Note that currently not *all* comments can be
kept when compression is on, because of dead
code removal or cascading statements into
sequences. [string]
--preamble Preamble to prepend to the output. You can use
this to insert a comment, for example for
licensing information. This will not be
parsed, but the source map will adjust for its
presence.
--stats Display operations run time on STDERR.
[boolean]
--acorn Use Acorn for parsing. [boolean]
--spidermonkey Assume input files are SpiderMonkey AST format
(as JSON). [boolean]
--self Build itself (UglifyJS2) as a library (implies
--wrap=UglifyJS --export-all) [boolean]
--wrap Embed everything in a big function, making the
“exports” and “global” variables available. You
need to pass an argument to this option to
specify the name that your module will take
when included in, say, a browser. [string]
--export-all Only used when --wrap, this tells UglifyJS to
add code to automatically export all globals.
[boolean]
--lint Display some scope warnings [boolean]
-v, --verbose Verbose [boolean]
-V, --version Print version number and exit. [boolean]
--noerr Don‘t throw an error for unknown options in -c,
-b or -m. [boolean]
对命令参数进行解释：
通过对命令行各种参数的解释，我们基本上知道了这些参数都是干什么的了，下面我就试一下。
写2个简单地JS文件，demo.js, main.js。
~ vi D:\workspace\javascript\nodejs-uglifyJS2\demo.js
‘use strict‘;
function hello(name){
if(name===‘fens.me‘){
return "Long time no see, "+name;
}
return "hello "+name;
}
console.log(hello(‘Conan‘));
console.log(hello(‘fens.me‘));
main.js
~ vi D:\workspace\javascript\nodejs-uglifyJS2\main.js
‘use strict‘;
function book(){
return [
{head:‘前言‘,page:‘/views/tpl/book-r1/preface.html‘,active:false},
{head:‘目录‘,page:‘/views/tpl/book-r1/contents.html‘,active:true},
{head:‘代码‘,page:‘/views/tpl/book-r1/code.html‘,active:false},
{head:‘试读‘,page:‘/views/tpl/book-r1/sample.html‘,active:false},
{head:‘勘误‘,page:‘/views/tpl/book-r1/mistake.html‘,active:false}
];
}
var tab=function(arr,idx){
for(var i=0;i<arr.length;i++){
arr[i].active = (idx==i?true:false);
}
return arr;
}
console.log(tab(book(),3));
接下来，用UglifyJS2命令进行操作，合并两个文件，对变量名用单字母替换，进行压缩，所有代码合并到一个函数，生成source map，指定source map来源网站。
D:\workspace\javascript\nodejs-uglifyJS2>uglifyjs main.js demo.js -o foo.min.js --source-map foo.min.js.map --source-map-root http://onbook.me -p 5 -c -m --wrap --export-all
在当前目录生成了2个新文件：foo.min.js.map, foo.min.js，分别查看这两个文件。
foo.min.js
!function(e,t){"use strict";function o(){return[{head:"前言",page:"/views/tpl/book-r1/preface.html",active:!1},{head:"目录",page:"/views/tpl/book-r1/contents.html",active:!0},{head:"代码",page:"/views/tpl/book-r1/code.html",active:!1},{head:"试读",page:"/views/tpl/book-r1/sample.html",active:!1},{head:"勘误",page:"/views/tpl/book-r1/mistake.html",active:!1}]}function n(e){return"fens.me"===e?"Long time no see, "+e:"hello "+e}t["true"]=e,console.log(a(o(),3));var a=function(e,t){for(var o=0;o
foo.min.js.map
{"version":3,"file":"foo.min.js","sources":["?"],"names":["exports","global","book","head","page","active","hello","name","console","log","tab","arr","idx","i","length","this"],"mappings":"CAAC,SAASA,EAASC,GAAnB,YAEA,SAASC,KACL,QACKC,KAAK,KAAKC,KAAK,kCAAkCC,QAAO,IACxDF,KAAK,KAAKC,KAAK,mCAAmCC,QAAO,IACzDF,KAAK,KAAKC,KAAK,+BAA+BC,QAAO,IACrDF,KAAK,KAAKC,KAAK,iCAAiCC,QAAO,IACvDF,KAAK,KAAKC,KAAK,kCAAkCC,QAAO,IANjE,QAASC,GAAMC,GACd,MAAU,YAAPA,EACK,qBAAqBA,EAEtB,SAASA,EANWN,EAAO,QAAUD,EAY7CQ,QAAQC,IAAIC,EAAIR,IAAO,GADvB,IAAIQ,GAAI,SAASC,EAAIC,GACpB,IAAI,GAAIC,GAAE,EAAEA,EAAEF,EAAIG,OAAOD,IACxBF,EAAIE,GAAGR,OAAUO,GAAKC,GAAE,GAAK,CAE9B,OAAOF,GAGRH,SAAQC,IAAIH,EAAM,UAClBE,QAAQC,IAAIH,EAAM,mBAjBTJ,UAAAI,QASLI,MAX8E,WAAW,MAAOK","sourceRoot":"http://onbook.me"}
通过一条简单的命令，就实现了对JS代码的合并、压缩等的操作，确实非常方便。
下载jquery-2.1.1.js文件自己压缩，并与官方的压缩文件进行对比。
# 下载
~ wget http://code.jquery.com/jquery-2.1.1.js
~ wget http://code.jquery.com/jquery-2.1.1.min.js
# 压缩
~ uglifyjs jquery-2.1.1.js -o jquery-2.1.1.min.uglifyjs2.js -p 5 -c -m
# 比较3个文件大小
~ ls -l
-rwx------ 1 4294967295 mkpasswd 247351 Jul 6 16:26 jquery-2.1.1.js
-rwx------ 1 4294967295 mkpasswd 84245 Jul 6 16:32 jquery-2.1.1.min.js
-rwx------ 1 4294967295 mkpasswd 84113 Jul 6 16:28 jquery-2.1.1.min.uglifyjs2.js
我在本地压缩的文件jquery-2.1.1.min.uglifyjs2.js，与jquery官司网下载的压缩文件jquery-2.1.1.min.js大小差不多，都在84KB左右。
另一种使用方式是，把UglifyJS2包放到程序中，通过API对JS文件或JS代码进行压缩。首先，新建一个NPM项目文件package.json，然后在是下载UglifyJS2依赖包。
新建文件package.json
~ vi D:\workspace\javascript\nodejs-uglifyJS2\package.json
{
"name": "nodejs-uglifyjs2",
"version": "0.0.1",
"description": "uglifyjs2",
"author": "Conan Zhang
",
"dependencies": {
}
}
下载UglifyJS2依赖包
D:\workspace\javascript\nodejs-uglifyJS2>npm install uglify-js --save
npm WARN package.json nodejs-uglifyjs2@0.0.1 No readme data!
npm http GET https://registry.npmjs.org/uglify-js
npm http 304 https://registry.npmjs.org/uglify-js
npm http GET https://registry.npmjs.org/async
npm http GET https://registry.npmjs.org/source-map
npm http GET https://registry.npmjs.org/optimist
npm http GET https://registry.npmjs.org/uglify-to-browserify
npm http 304 https://registry.npmjs.org/uglify-to-browserify
npm http 304 https://registry.npmjs.org/optimist
npm http 304 https://registry.npmjs.org/async
npm http 304 https://registry.npmjs.org/source-map
npm http GET https://registry.npmjs.org/wordwrap
npm http GET https://registry.npmjs.org/amdefine
npm http 304 https://registry.npmjs.org/wordwrap
npm http 304 https://registry.npmjs.org/amdefine
uglify-js@2.4.14 node_modules\uglify-js
├── uglify-to-browserify@1.0.2
├── async@0.2.10
├── optimist@0.3.7 (wordwrap@0.0.2)
└── source-map@0.1.34 (amdefine@0.1.0)
我们新建一个文件uglify2.js，用于编写程序。
~ vi D:\workspace\javascript\nodejs-uglifyJS2\uglify2.js
‘use strict‘;
var UglifyJS = require(‘uglify-js‘);
//代码压缩
var result = UglifyJS.minify("var b = function () {};", {fromString: true});
console.log("\n===========================");
console.log(result);
//文件压缩
result = UglifyJS.minify(["demo.js"]);
console.log("\n===========================");
console.log(result.code);
//多文件压缩，指定source map和网站来源
result = UglifyJS.minify(["main.js","demo.js"],{
outSourceMap: "out.js.map",
sourceRoot: "http://onbook.me",
mangle:true
});
console.log("\n===========================");
console.log(result.code);
console.log(result.map);
程序输出：
D:\workspace\javascript\nodejs-uglifyJS2>node uglify2.js
===========================
{ code: ‘var b=function(){};‘, map: ‘null‘ }
===========================
"use strict";function hello(e){return"fens.me"===e?"Long time no see, "+e:"hello "+e}var tab=function(e,o){for(var n=0;n
<e.length;n++)e[n].active=o==n?!0:!1;return e};console.log(hello("Conan")),console.log(hello("fens.me"));
===========================
"use strict";function book(){return[{head:"前言",page:"/views/tpl/book-r1/preface.html",active:!1},{head:"目录",page:"/v
iews/tpl/book-r1/contents.html",active:!0},{head:"代码",page:"/views/tpl/book-r1/code.html",active:!1},{head:"试读",page
:"/views/tpl/book-r1/sample.html",active:!1},{head:"勘误",page:"/views/tpl/book-r1/mistake.html",active:!1}]}function he
llo(e){return"fens.me"===e?"Long time no see, "+e:"hello "+e}console.log(tab(book(),3));var tab=function(e,o){for(var t=
0;t<e.length;t++)e[t].active=o==t?!0:!1;return e};console.log(hello("Conan")),console.log(hello("fens.me"));
//# sourceMappingURL=out.js.map
{"version":3,"file":"out.js.map","sources":["main.js","demo.js"],"names":["book","head","page","active","hello","name","
console","log","tab","arr","idx","i","length"],"mappings":"AAAA,YAEA,SAASA,QACL,QACKC,KAAK,KAAKC,KAAK,kCAAkCC,QAAO,IACxD
F,KAAK,KAAKC,KAAK,mCAAmCC,QAAO,IACzDF,KAAK,KAAKC,KAAK,+BAA+BC,QAAO,IACrDF,KAAK,KAAKC,KAAK,iCAAiCC,QAAO,IACvDF,KAAK,KAAKC
,KAAK,kCAAkCC,QAAO,ICNjE,QAASC,OAAMC,GACd,MAAU,YAAPA,EACK,qBAAqBA,EAEtB,SAASA,EDMjBC,QAAQC,IAAIC,IAAIR,OAAO,GCDvB,IAAIQ,
KAAI,SAASC,EAAIC,GACpB,IAAI,GAAIC,GAAE,EAAEA,EAAEF,EAAIG,OAAOD,IACxBF,EAAIE,GAAGR,OAAUO,GAAKC,GAAE,GAAK,CAE9B,OAAOF,GAGR
H,SAAQC,IAAIH,MAAM,UAClBE,QAAQC,IAAIH,MAAM","sourceRoot":"http://onbook.me"}
我们看到用操作uglifyJS2包的API，还是挺简单的，如果对AST树有遍历需求，API提供了非常实用的函数支持。
不过我在测试API过程中,发现有2个问题。
通过本文的介绍，我们基本上了解了uglifyJS2包的功能和使用方法，然后就可以放心大胆地对JS代码进行压缩了。在实际的前端项目中，一般不用自己配置uglifyJS2包，而是通过grunt来调用uglifyJS2进行代码发布前的压缩，关于grunt使用，请参考文章： grunt让Nodejs规范起来 。
原文：http://www.cnblogs.com/zzsdream/p/5674866.html