UglifyJS 2
==========
[![Build Status](https://travis-ci.org/mishoo/UglifyJS2.svg)](https://travis-ci.org/mishoo/UglifyJS2)
UglifyJS is a JavaScript parser, minifier, compressor or beautifier toolkit.
This page documents the command line utility. For
[API and internals documentation see my website](http://lisperator.net/uglifyjs/).
There's also an
[in-browser online demo](http://lisperator.net/uglifyjs/#demo) (for Firefox,
Chrome and probably Safari).
#### Note:
- `uglify-js` only supports ECMAScript 5 (ES5).
- Support for `const` is [present but incomplete](#support-for-const), and may not be
transformed properly.
- Those wishing to minify ES2015+ (ES6+) should use the `npm` package [**uglify-es**](https://github.com/mishoo/UglifyJS2/tree/harmony).
Install
-------
First make sure you have installed the latest version of [node.js](http://nodejs.org/)
(You may need to restart your computer after this step).
From NPM for use as a command line app:
npm install uglify-js -g
From NPM for programmatic use:
npm install uglify-js
Usage
-----
uglifyjs [input files] [options]
UglifyJS2 can take multiple input files. It's recommended that you pass the
input files first, then pass the options. UglifyJS will parse input files
in sequence and apply any compression options. The files are parsed in the
same global scope, that is, a reference from a file to some
variable/function declared in another file will be matched properly.
If you want to read from STDIN instead, pass a single dash instead of input
files.
If you wish to pass your options before the input files, separate the two with
a double dash to prevent input files being used as option arguments:
uglifyjs --compress --mangle -- input.js
The available options are:
```
--source-map Specify an output file where to generate source
map.
--source-map-root The path to the original source to be included
in the source map.
--source-map-url The path to the source map to be added in //#
sourceMappingURL. Defaults to the value passed
with --source-map.
--source-map-include-sources Pass this flag if you want to include the
content of source files in the source map as
sourcesContent property.
--source-map-inline Write base64-encoded source map to the end of js output.
--in-source-map Input source map, useful if you're compressing
JS that was generated from some other original
code. Specify "inline" if the source map is included
inline with the sources.
--screw-ie8 Use this flag if you don't wish to support
Internet Explorer 6/7/8.
By default UglifyJS will not try to be IE-proof.
--support-ie8 Use this flag to support Internet Explorer 6/7/8.
Equivalent to setting `screw_ie8: false` in `minify()`
for `compress`, `mangle` and `output` options.
--expr Parse a single expression, rather than a
program (for parsing JSON)
-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.
-o, --output Output file (default STDOUT).
-b, --beautify Beautify output/specify output options.
-m, --mangle Mangle names/pass mangler options.
-r, --reserved Reserved names to exclude from mangling.
-c, --compress Enable compressor/pass compressor options, e.g.
`-c 'if_return=false,pure_funcs=["Math.pow","console.log"]'`
Use `-c` with no argument to enable default compression
options.
-d, --define Global definitions
-e, --enclose Embed everything in a big function, with a
configurable parameter/argument list.
--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 like `/foo/` or `/^!/` to
keep only matching comments.
Note that currently not *all* comments can be
kept when compression is on, because of dead
code removal or cascading statements into
sequences.
--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.
--acorn Use Acorn for parsing.
--spidermonkey Assume input files are SpiderMonkey AST format
(as JSON).
--self Build itself (UglifyJS2) as a library (implies
--wrap=UglifyJS --export-all)
--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.
--export-all Only used when --wrap, this tells UglifyJS to
add code to automatically export all globals.
--lint Display some scope warnings
-v, --verbose Verbose
-V, --version Print version number and exit.
--noerr Don't throw an error for unknown options in -c,
-b or -m.
--bare-returns Allow return outside of functions. Useful when
minifying CommonJS modules and Userscripts that
may be anonymous function wrapped (IIFE) by the
.user.js engine `caller`.
--keep-fnames Do not mangle/drop function names. Useful for
code relying on Function.prototype.name.
--reserved-file File containing reserved names
--reserve-domprops Make (most?) DOM properties reserved for
--mangle-props
--mangle-props Mangle property names (default `0`). Set to
`true` or `1` to mangle all property names. Set
to `unquoted` or `2` to onl