These pages are old. They apply to UglifyJS v2. Version 3 has evolved a lot in the mean time to support most of ES6. Please check the documentation in the official repository for up-to-date information. Big thanks to all contributors, especially to Alex Lam S.L., who has maintained this project for years!
- A compressor (optimizer) — it uses the transformer API to optimize an AST into a smaller one.
- A mangler — reduce names of local variables to (usually) single-letters.
- A scope analyzer, which is a tool that augments the AST with information about where variables are defined/referenced etc.
- A tree walker — a simple API allowing you to do something on every node in the AST.
- A tree transformer — another API intended to transform the tree.
All the above utilities and APIs are defined in ~6500 lines of code (except for the effective generation of the source-map, which is handled by the source-map module). Compared to alternatives, UglifyJS is pretty small.
These pages document the internals of UglifyJS. For a documentation of the command-line options please see the README.
Installing (for NodeJS)
You can install UglifyJS from NPM:
npm install uglify-js
but you can also use the Git repository if you feel adventurous:
git clone git://github.com/mishoo/UglifyJS2.git
npm link .
Building for the browser
Once you installed it for NodeJS, UglifyJS2 provides a quick way to build itself for the browser:
uglifyjs --self -c -m -o /tmp/uglifyjs.js
Now you have it in /tmp/uglifyjs.js and can include that single file in a browser. If you need source maps you'll also have to include the Mozilla source-map module. details to be clarified
UglifyJS is written in “classic style”, so to say — it's not using the
CommonJS module system (I find it more of an annoyance than of real help,
especially for prototyping/development). To load it in NodeJS there's a
single file that needs to be require-d: tools/node.js.
If you installed it with npm install or npm link as
mentioned above, then this file is loaded when you say
UglifyJS = require("uglify-js2"). This single file will load all the
others in a separate execution context, so you should not worry about
messing your global environment, and it returns a single object where all
the global definitions in UglifyJS are exported.
Here are some stats showing where UglifyJS2 stands compared to other minifiers. Show charts.
JS compressor of world fame.Open demo
- Code generator
- The AST structure
- SpiderMonkey AST
- Scope analysis
- AST walker
- AST transformer
- UglifyJS on Github
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/** May the source-map be with you! **/