e645ba84cf
The option added in fbbaa42ee5 wasn't
being respected inside object literals, so quoted property names would
still be stripped out with this option.
This is mostly a corner-case, but useful when the output is passed to
something like the Closure compiler, where quoted property names can be
used to prevent mangling.
845 lines
34 KiB
Markdown
845 lines
34 KiB
Markdown
UglifyJS 2
|
||
==========
|
||
[](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/).
|
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There's also an
|
||
[in-browser online demo](http://lisperator.net/uglifyjs/#demo) (for Firefox,
|
||
Chrome and probably Safari).
|
||
|
||
Install
|
||
-------
|
||
|
||
First make sure you have installed the latest version of [node.js](http://nodejs.org/)
|
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(You may need to restart your computer after this step).
|
||
|
||
From NPM for use as a command line app:
|
||
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||
npm install uglify-js -g
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|
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From NPM for programmatic use:
|
||
|
||
npm install uglify-js
|
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|
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From Git:
|
||
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git clone git://github.com/mishoo/UglifyJS2.git
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cd UglifyJS2
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npm link .
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|
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Usage
|
||
-----
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uglifyjs [input files] [options]
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|
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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.
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If you want to read from STDIN instead, pass a single dash instead of input
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||
files.
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If you wish to pass your options before the input files, separate the two with
|
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a double dash to prevent input files being used as option arguments:
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||
|
||
uglifyjs --compress --mangle -- input.js
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|
||
The available options are:
|
||
|
||
```
|
||
--source-map Specify an output file where to generate source
|
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map.
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||
--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 //#
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||
sourceMappingURL. Defaults to the value passed
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||
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.
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||
--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
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||
compliance with Internet Explorer 6-8 quirks
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||
(by default UglifyJS will try to be IE-proof).
|
||
--expr Parse a single expression, rather than a
|
||
program (for parsing JSON)
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||
-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
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||
relative, which will make UglifyJS figure out
|
||
itself the relative paths between original
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sources, the source map and the output file.
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||
-o, --output Output file (default STDOUT).
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||
-b, --beautify Beautify output/specify output options.
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||
-m, --mangle Mangle names/pass mangler options.
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||
-r, --reserved Reserved names to exclude from mangling.
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||
-c, --compress Enable compressor/pass compressor options. Pass
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options like -c
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hoist_vars=false,if_return=false. Use -c with
|
||
no argument to use the default compression
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options.
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-d, --define Global definitions
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||
-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
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||
- 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
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||
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 only mangle unquoted
|
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property names. Mode `2` also enables the
|
||
`keep_quoted_props` beautifier option to
|
||
preserve the quotes around property names and
|
||
disables the `properties` compressor option to
|
||
prevent rewriting quoted properties with dot
|
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notation. You can override these by setting
|
||
them explicitly on the command line.
|
||
--mangle-regex Only mangle property names matching the regex
|
||
--name-cache File to hold mangled names mappings
|
||
--pure-funcs List of functions that can be safely removed if
|
||
their return value is not used [array]
|
||
```
|
||
|
||
Specify `--output` (`-o`) to declare the output file. Otherwise the output
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||
goes to STDOUT.
|
||
|
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## Source map options
|
||
|
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UglifyJS2 can generate a source map file, which is highly useful for
|
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debugging your compressed JavaScript. To get a source map, pass
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`--source-map output.js.map` (full path to the file where you want the
|
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source map dumped).
|
||
|
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Additionally you might need `--source-map-root` to pass the URL where the
|
||
original files can be found. In case you are passing full paths to input
|
||
files to UglifyJS, you can use `--prefix` (`-p`) to specify the number of
|
||
directories to drop from the path prefix when declaring files in the source
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map.
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|
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For example:
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|
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uglifyjs /home/doe/work/foo/src/js/file1.js \
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/home/doe/work/foo/src/js/file2.js \
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-o foo.min.js \
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--source-map foo.min.js.map \
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--source-map-root http://foo.com/src \
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-p 5 -c -m
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|
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The above will compress and mangle `file1.js` and `file2.js`, will drop the
|
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output in `foo.min.js` and the source map in `foo.min.js.map`. The source
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mapping will refer to `http://foo.com/src/js/file1.js` and
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`http://foo.com/src/js/file2.js` (in fact it will list `http://foo.com/src`
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as the source map root, and the original files as `js/file1.js` and
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`js/file2.js`).
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|
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### Composed source map
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|
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When you're compressing JS code that was output by a compiler such as
|
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CoffeeScript, mapping to the JS code won't be too helpful. Instead, you'd
|
||
like to map back to the original code (i.e. CoffeeScript). UglifyJS has an
|
||
option to take an input source map. Assuming you have a mapping from
|
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CoffeeScript → compiled JS, UglifyJS can generate a map from CoffeeScript →
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||
compressed JS by mapping every token in the compiled JS to its original
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||
location.
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||
|
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To use this feature you need to pass `--in-source-map
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/path/to/input/source.map`. Normally the input source map should also point
|
||
to the file containing the generated JS, so if that's correct you can omit
|
||
input files from the command line.
|
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|
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## Mangler options
|
||
|
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To enable the mangler you need to pass `--mangle` (`-m`). The following
|
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(comma-separated) options are supported:
|
||
|
||
- `toplevel` — mangle names declared in the toplevel scope (disabled by
|
||
default).
|
||
|
||
- `eval` — mangle names visible in scopes where `eval` or `with` are used
|
||
(disabled by default).
|
||
|
||
When mangling is enabled but you want to prevent certain names from being
|
||
mangled, you can declare those names with `--reserved` (`-r`) — pass a
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comma-separated list of names. For example:
|
||
|
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uglifyjs ... -m -r '$,require,exports'
|
||
|
||
to prevent the `require`, `exports` and `$` names from being changed.
|
||
|
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### Mangling property names (`--mangle-props`)
|
||
|
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**Note:** this will probably break your code. Mangling property names is a
|
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separate step, different from variable name mangling. Pass
|
||
`--mangle-props`. It will mangle all properties that are seen in some
|
||
object literal, or that are assigned to. For example:
|
||
|
||
```js
|
||
var x = {
|
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foo: 1
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};
|
||
|
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x.bar = 2;
|
||
x["baz"] = 3;
|
||
x[condition ? "moo" : "boo"] = 4;
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console.log(x.something());
|
||
```
|
||
|
||
In the above code, `foo`, `bar`, `baz`, `moo` and `boo` will be replaced
|
||
with single characters, while `something()` will be left as is.
|
||
|
||
In order for this to be of any use, we should avoid mangling standard JS
|
||
names. For instance, if your code would contain `x.length = 10`, then
|
||
`length` becomes a candidate for mangling and it will be mangled throughout
|
||
the code, regardless if it's being used as part of your own objects or
|
||
accessing an array's length. To avoid that, you can use `--reserved-file`
|
||
to pass a filename that should contain the names to be excluded from
|
||
mangling. This file can be used both for excluding variable names and
|
||
property names. It could look like this, for example:
|
||
|
||
```js
|
||
{
|
||
"vars": [ "define", "require", ... ],
|
||
"props": [ "length", "prototype", ... ]
|
||
}
|
||
```
|
||
|
||
`--reserved-file` can be an array of file names (either a single
|
||
comma-separated argument, or you can pass multiple `--reserved-file`
|
||
arguments) — in this case it will exclude names from all those files.
|
||
|
||
A default exclusion file is provided in `tools/domprops.json` which should
|
||
cover most standard JS and DOM properties defined in various browsers. Pass
|
||
`--reserve-domprops` to read that in.
|
||
|
||
You can also use a regular expression to define which property names should be
|
||
mangled. For example, `--mangle-regex="/^_/"` will only mangle property names
|
||
that start with an underscore.
|
||
|
||
When you compress multiple files using this option, in order for them to
|
||
work together in the end we need to ensure somehow that one property gets
|
||
mangled to the same name in all of them. For this, pass `--name-cache
|
||
filename.json` and UglifyJS will maintain these mappings in a file which can
|
||
then be reused. It should be initially empty. Example:
|
||
|
||
```
|
||
rm -f /tmp/cache.json # start fresh
|
||
uglifyjs file1.js file2.js --mangle-props --name-cache /tmp/cache.json -o part1.js
|
||
uglifyjs file3.js file4.js --mangle-props --name-cache /tmp/cache.json -o part2.js
|
||
```
|
||
|
||
Now, `part1.js` and `part2.js` will be consistent with each other in terms
|
||
of mangled property names.
|
||
|
||
Using the name cache is not necessary if you compress all your files in a
|
||
single call to UglifyJS.
|
||
|
||
## Compressor options
|
||
|
||
You need to pass `--compress` (`-c`) to enable the compressor. Optionally
|
||
you can pass a comma-separated list of options. Options are in the form
|
||
`foo=bar`, or just `foo` (the latter implies a boolean option that you want
|
||
to set `true`; it's effectively a shortcut for `foo=true`).
|
||
|
||
- `sequences` -- join consecutive simple statements using the comma operator
|
||
|
||
- `properties` -- rewrite property access using the dot notation, for
|
||
example `foo["bar"] → foo.bar`
|
||
|
||
- `dead_code` -- remove unreachable code
|
||
|
||
- `drop_debugger` -- remove `debugger;` statements
|
||
|
||
- `unsafe` (default: false) -- apply "unsafe" transformations (discussion below)
|
||
|
||
- `unsafe_comps` (default: false) -- Reverse `<` and `<=` to `>` and `>=` to
|
||
allow improved compression. This might be unsafe when an at least one of two
|
||
operands is an object with computed values due the use of methods like `get`,
|
||
or `valueOf`. This could cause change in execution order after operands in the
|
||
comparison are switching. Compression only works if both `comparisons` and
|
||
`unsafe_comps` are both set to true.
|
||
|
||
- `conditionals` -- apply optimizations for `if`-s and conditional
|
||
expressions
|
||
|
||
- `comparisons` -- apply certain optimizations to binary nodes, for example:
|
||
`!(a <= b) → a > b` (only when `unsafe_comps`), attempts to negate binary
|
||
nodes, e.g. `a = !b && !c && !d && !e → a=!(b||c||d||e)` etc.
|
||
|
||
- `evaluate` -- attempt to evaluate constant expressions
|
||
|
||
- `booleans` -- various optimizations for boolean context, for example `!!a
|
||
? b : c → a ? b : c`
|
||
|
||
- `loops` -- optimizations for `do`, `while` and `for` loops when we can
|
||
statically determine the condition
|
||
|
||
- `unused` -- drop unreferenced functions and variables
|
||
|
||
- `hoist_funs` -- hoist function declarations
|
||
|
||
- `hoist_vars` (default: false) -- hoist `var` declarations (this is `false`
|
||
by default because it seems to increase the size of the output in general)
|
||
|
||
- `if_return` -- optimizations for if/return and if/continue
|
||
|
||
- `join_vars` -- join consecutive `var` statements
|
||
|
||
- `cascade` -- small optimization for sequences, transform `x, x` into `x`
|
||
and `x = something(), x` into `x = something()`
|
||
|
||
- `collapse_vars` -- default `false`. Collapse single-use `var` and `const`
|
||
definitions when possible.
|
||
|
||
- `warnings` -- display warnings when dropping unreachable code or unused
|
||
declarations etc.
|
||
|
||
- `negate_iife` -- negate "Immediately-Called Function Expressions"
|
||
where the return value is discarded, to avoid the parens that the
|
||
code generator would insert.
|
||
|
||
- `pure_getters` -- the default is `false`. If you pass `true` for
|
||
this, UglifyJS will assume that object property access
|
||
(e.g. `foo.bar` or `foo["bar"]`) doesn't have any side effects.
|
||
|
||
- `pure_funcs` -- default `null`. You can pass an array of names and
|
||
UglifyJS will assume that those functions do not produce side
|
||
effects. DANGER: will not check if the name is redefined in scope.
|
||
An example case here, for instance `var q = Math.floor(a/b)`. If
|
||
variable `q` is not used elsewhere, UglifyJS will drop it, but will
|
||
still keep the `Math.floor(a/b)`, not knowing what it does. You can
|
||
pass `pure_funcs: [ 'Math.floor' ]` to let it know that this
|
||
function won't produce any side effect, in which case the whole
|
||
statement would get discarded. The current implementation adds some
|
||
overhead (compression will be slower).
|
||
|
||
- `drop_console` -- default `false`. Pass `true` to discard calls to
|
||
`console.*` functions.
|
||
|
||
- `keep_fargs` -- default `true`. Prevents the
|
||
compressor from discarding unused function arguments. You need this
|
||
for code which relies on `Function.length`.
|
||
|
||
- `keep_fnames` -- default `false`. Pass `true` to prevent the
|
||
compressor from mangling/discarding function names. Useful for code relying on
|
||
`Function.prototype.name`.
|
||
|
||
- `passes` -- default `1`. Number of times to run compress. Use an
|
||
integer argument larger than 1 to further reduce code size in some cases.
|
||
Note: raising the number of passes will increase uglify compress time.
|
||
|
||
### The `unsafe` option
|
||
|
||
It enables some transformations that *might* break code logic in certain
|
||
contrived cases, but should be fine for most code. You might want to try it
|
||
on your own code, it should reduce the minified size. Here's what happens
|
||
when this flag is on:
|
||
|
||
- `new Array(1, 2, 3)` or `Array(1, 2, 3)` → `[ 1, 2, 3 ]`
|
||
- `new Object()` → `{}`
|
||
- `String(exp)` or `exp.toString()` → `"" + exp`
|
||
- `new Object/RegExp/Function/Error/Array (...)` → we discard the `new`
|
||
- `typeof foo == "undefined"` → `foo === void 0`
|
||
- `void 0` → `undefined` (if there is a variable named "undefined" in
|
||
scope; we do it because the variable name will be mangled, typically
|
||
reduced to a single character)
|
||
|
||
### Conditional compilation
|
||
|
||
You can use the `--define` (`-d`) switch in order to declare global
|
||
variables that UglifyJS will assume to be constants (unless defined in
|
||
scope). For example if you pass `--define DEBUG=false` then, coupled with
|
||
dead code removal UglifyJS will discard the following from the output:
|
||
```javascript
|
||
if (DEBUG) {
|
||
console.log("debug stuff");
|
||
}
|
||
```
|
||
|
||
UglifyJS will warn about the condition being always false and about dropping
|
||
unreachable code; for now there is no option to turn off only this specific
|
||
warning, you can pass `warnings=false` to turn off *all* warnings.
|
||
|
||
Another way of doing that is to declare your globals as constants in a
|
||
separate file and include it into the build. For example you can have a
|
||
`build/defines.js` file with the following:
|
||
```javascript
|
||
const DEBUG = false;
|
||
const PRODUCTION = true;
|
||
// Alternative for environments that don't support `const`
|
||
/** @const */ var STAGING = false;
|
||
// etc.
|
||
```
|
||
|
||
and build your code like this:
|
||
|
||
uglifyjs build/defines.js js/foo.js js/bar.js... -c
|
||
|
||
UglifyJS will notice the constants and, since they cannot be altered, it
|
||
will evaluate references to them to the value itself and drop unreachable
|
||
code as usual. The build will contain the `const` declarations if you use
|
||
them. If you are targeting < ES6 environments, use `/** @const */ var`.
|
||
|
||
<a name="codegen-options"></a>
|
||
|
||
#### Conditional compilation, API
|
||
You can also use conditional compilation via the programmatic API. With the difference that the
|
||
property name is `global_defs` and is a compressor property:
|
||
|
||
```js
|
||
uglifyJS.minify([ "input.js"], {
|
||
compress: {
|
||
dead_code: true,
|
||
global_defs: {
|
||
DEBUG: false
|
||
}
|
||
}
|
||
});
|
||
```
|
||
|
||
## Beautifier options
|
||
|
||
The code generator tries to output shortest code possible by default. In
|
||
case you want beautified output, pass `--beautify` (`-b`). Optionally you
|
||
can pass additional arguments that control the code output:
|
||
|
||
- `beautify` (default `true`) -- whether to actually beautify the output.
|
||
Passing `-b` will set this to true, but you might need to pass `-b` even
|
||
when you want to generate minified code, in order to specify additional
|
||
arguments, so you can use `-b beautify=false` to override it.
|
||
- `indent-level` (default 4)
|
||
- `indent-start` (default 0) -- prefix all lines by that many spaces
|
||
- `quote-keys` (default `false`) -- pass `true` to quote all keys in literal
|
||
objects
|
||
- `space-colon` (default `true`) -- insert a space after the colon signs
|
||
- `ascii-only` (default `false`) -- escape Unicode characters in strings and
|
||
regexps (affects directives with non-ascii characters becoming invalid)
|
||
- `inline-script` (default `false`) -- escape the slash in occurrences of
|
||
`</script` in strings
|
||
- `width` (default 80) -- only takes effect when beautification is on, this
|
||
specifies an (orientative) line width that the beautifier will try to
|
||
obey. It refers to the width of the line text (excluding indentation).
|
||
It doesn't work very well currently, but it does make the code generated
|
||
by UglifyJS more readable.
|
||
- `max-line-len` (default 32000) -- maximum line length (for uglified code)
|
||
- `bracketize` (default `false`) -- always insert brackets in `if`, `for`,
|
||
`do`, `while` or `with` statements, even if their body is a single
|
||
statement.
|
||
- `semicolons` (default `true`) -- separate statements with semicolons. If
|
||
you pass `false` then whenever possible we will use a newline instead of a
|
||
semicolon, leading to more readable output of uglified code (size before
|
||
gzip could be smaller; size after gzip insignificantly larger).
|
||
- `preamble` (default `null`) -- when passed it must be a string and
|
||
it will be prepended to the output literally. The source map will
|
||
adjust for this text. Can be used to insert a comment containing
|
||
licensing information, for example.
|
||
- `quote_style` (default `0`) -- preferred quote style for strings (affects
|
||
quoted property names and directives as well):
|
||
- `0` -- prefers double quotes, switches to single quotes when there are
|
||
more double quotes in the string itself.
|
||
- `1` -- always use single quotes
|
||
- `2` -- always use double quotes
|
||
- `3` -- always use the original quotes
|
||
- `keep_quoted_props` (default `false`) -- when turned on, prevents stripping
|
||
quotes from property names in object literals.
|
||
|
||
### Keeping copyright notices or other comments
|
||
|
||
You can pass `--comments` to retain certain comments in the output. By
|
||
default it will keep JSDoc-style comments that contain "@preserve",
|
||
"@license" or "@cc_on" (conditional compilation for IE). You can pass
|
||
`--comments all` to keep all the comments, or a valid JavaScript regexp to
|
||
keep only comments that match this regexp. For example `--comments
|
||
'/foo|bar/'` will keep only comments that contain "foo" or "bar".
|
||
|
||
Note, however, that there might be situations where comments are lost. For
|
||
example:
|
||
```javascript
|
||
function f() {
|
||
/** @preserve Foo Bar */
|
||
function g() {
|
||
// this function is never called
|
||
}
|
||
return something();
|
||
}
|
||
```
|
||
|
||
Even though it has "@preserve", the comment will be lost because the inner
|
||
function `g` (which is the AST node to which the comment is attached to) is
|
||
discarded by the compressor as not referenced.
|
||
|
||
The safest comments where to place copyright information (or other info that
|
||
needs to be kept in the output) are comments attached to toplevel nodes.
|
||
|
||
## Support for the SpiderMonkey AST
|
||
|
||
UglifyJS2 has its own abstract syntax tree format; for
|
||
[practical reasons](http://lisperator.net/blog/uglifyjs-why-not-switching-to-spidermonkey-ast/)
|
||
we can't easily change to using the SpiderMonkey AST internally. However,
|
||
UglifyJS now has a converter which can import a SpiderMonkey AST.
|
||
|
||
For example [Acorn][acorn] is a super-fast parser that produces a
|
||
SpiderMonkey AST. It has a small CLI utility that parses one file and dumps
|
||
the AST in JSON on the standard output. To use UglifyJS to mangle and
|
||
compress that:
|
||
|
||
acorn file.js | uglifyjs --spidermonkey -m -c
|
||
|
||
The `--spidermonkey` option tells UglifyJS that all input files are not
|
||
JavaScript, but JS code described in SpiderMonkey AST in JSON. Therefore we
|
||
don't use our own parser in this case, but just transform that AST into our
|
||
internal AST.
|
||
|
||
### Use Acorn for parsing
|
||
|
||
More for fun, I added the `--acorn` option which will use Acorn to do all
|
||
the parsing. If you pass this option, UglifyJS will `require("acorn")`.
|
||
|
||
Acorn is really fast (e.g. 250ms instead of 380ms on some 650K code), but
|
||
converting the SpiderMonkey tree that Acorn produces takes another 150ms so
|
||
in total it's a bit more than just using UglifyJS's own parser.
|
||
|
||
### Using UglifyJS to transform SpiderMonkey AST
|
||
|
||
Now you can use UglifyJS as any other intermediate tool for transforming
|
||
JavaScript ASTs in SpiderMonkey format.
|
||
|
||
Example:
|
||
|
||
```javascript
|
||
function uglify(ast, options, mangle) {
|
||
// Conversion from SpiderMonkey AST to internal format
|
||
var uAST = UglifyJS.AST_Node.from_mozilla_ast(ast);
|
||
|
||
// Compression
|
||
uAST.figure_out_scope();
|
||
uAST = uAST.transform(UglifyJS.Compressor(options));
|
||
|
||
// Mangling (optional)
|
||
if (mangle) {
|
||
uAST.figure_out_scope();
|
||
uAST.compute_char_frequency();
|
||
uAST.mangle_names();
|
||
}
|
||
|
||
// Back-conversion to SpiderMonkey AST
|
||
return uAST.to_mozilla_ast();
|
||
}
|
||
```
|
||
|
||
Check out
|
||
[original blog post](http://rreverser.com/using-mozilla-ast-with-uglifyjs/)
|
||
for details.
|
||
|
||
API Reference
|
||
-------------
|
||
|
||
Assuming installation via NPM, you can load UglifyJS in your application
|
||
like this:
|
||
```javascript
|
||
var UglifyJS = require("uglify-js");
|
||
```
|
||
|
||
It exports a lot of names, but I'll discuss here the basics that are needed
|
||
for parsing, mangling and compressing a piece of code. The sequence is (1)
|
||
parse, (2) compress, (3) mangle, (4) generate output code.
|
||
|
||
### The simple way
|
||
|
||
There's a single toplevel function which combines all the steps. If you
|
||
don't need additional customization, you might want to go with `minify`.
|
||
Example:
|
||
```javascript
|
||
var result = UglifyJS.minify("/path/to/file.js");
|
||
console.log(result.code); // minified output
|
||
// if you need to pass code instead of file name
|
||
var result = UglifyJS.minify("var b = function () {};", {fromString: true});
|
||
```
|
||
|
||
You can also compress multiple files:
|
||
```javascript
|
||
var result = UglifyJS.minify([ "file1.js", "file2.js", "file3.js" ]);
|
||
console.log(result.code);
|
||
```
|
||
|
||
To generate a source map:
|
||
```javascript
|
||
var result = UglifyJS.minify([ "file1.js", "file2.js", "file3.js" ], {
|
||
outSourceMap: "out.js.map"
|
||
});
|
||
console.log(result.code); // minified output
|
||
console.log(result.map);
|
||
```
|
||
|
||
Note that the source map is not saved in a file, it's just returned in
|
||
`result.map`. The value passed for `outSourceMap` is only used to set the
|
||
`file` attribute in the source map (see [the spec][sm-spec]).
|
||
|
||
You can also specify sourceRoot property to be included in source map:
|
||
```javascript
|
||
var result = UglifyJS.minify([ "file1.js", "file2.js", "file3.js" ], {
|
||
outSourceMap: "out.js.map",
|
||
sourceRoot: "http://example.com/src"
|
||
});
|
||
```
|
||
|
||
If you're compressing compiled JavaScript and have a source map for it, you
|
||
can use the `inSourceMap` argument:
|
||
```javascript
|
||
var result = UglifyJS.minify("compiled.js", {
|
||
inSourceMap: "compiled.js.map",
|
||
outSourceMap: "minified.js.map"
|
||
});
|
||
// same as before, it returns `code` and `map`
|
||
```
|
||
|
||
If your input source map is not in a file, you can pass it in as an object
|
||
using the `inSourceMap` argument:
|
||
|
||
```javascript
|
||
var result = UglifyJS.minify("compiled.js", {
|
||
inSourceMap: JSON.parse(my_source_map_string),
|
||
outSourceMap: "minified.js.map"
|
||
});
|
||
```
|
||
|
||
The `inSourceMap` is only used if you also request `outSourceMap` (it makes
|
||
no sense otherwise).
|
||
|
||
Other options:
|
||
|
||
- `warnings` (default `false`) — pass `true` to display compressor warnings.
|
||
|
||
- `fromString` (default `false`) — if you pass `true` then you can pass
|
||
JavaScript source code, rather than file names.
|
||
|
||
- `mangle` — pass `false` to skip mangling names.
|
||
|
||
- `mangleProperties` (default `false`) — pass an object to specify custom
|
||
mangle property options.
|
||
|
||
- `output` (default `null`) — pass an object if you wish to specify
|
||
additional [output options][codegen]. The defaults are optimized
|
||
for best compression.
|
||
|
||
- `compress` (default `{}`) — pass `false` to skip compressing entirely.
|
||
Pass an object to specify custom [compressor options][compressor].
|
||
|
||
- `parse` (default {}) — pass an object if you wish to specify some
|
||
additional [parser options][parser]. (not all options available... see below)
|
||
|
||
##### mangleProperties options
|
||
|
||
- `regex` — Pass a RegExp to only mangle certain names (maps to the `--mangle-regex` CLI arguments option)
|
||
- `ignore_quoted` – Only mangle unquoted property names (maps to the `--mangle-props 2` CLI arguments option)
|
||
|
||
We could add more options to `UglifyJS.minify` — if you need additional
|
||
functionality please suggest!
|
||
|
||
### The hard way
|
||
|
||
Following there's more detailed API info, in case the `minify` function is
|
||
too simple for your needs.
|
||
|
||
#### The parser
|
||
```javascript
|
||
var toplevel_ast = UglifyJS.parse(code, options);
|
||
```
|
||
|
||
`options` is optional and if present it must be an object. The following
|
||
properties are available:
|
||
|
||
- `strict` — disable automatic semicolon insertion and support for trailing
|
||
comma in arrays and objects
|
||
- `bare_returns` — Allow return outside of functions. (maps to the
|
||
`--bare-returns` CLI arguments option and available to `minify` `parse`
|
||
other options object)
|
||
- `filename` — the name of the file where this code is coming from
|
||
- `toplevel` — a `toplevel` node (as returned by a previous invocation of
|
||
`parse`)
|
||
|
||
The last two options are useful when you'd like to minify multiple files and
|
||
get a single file as the output and a proper source map. Our CLI tool does
|
||
something like this:
|
||
```javascript
|
||
var toplevel = null;
|
||
files.forEach(function(file){
|
||
var code = fs.readFileSync(file, "utf8");
|
||
toplevel = UglifyJS.parse(code, {
|
||
filename: file,
|
||
toplevel: toplevel
|
||
});
|
||
});
|
||
```
|
||
|
||
After this, we have in `toplevel` a big AST containing all our files, with
|
||
each token having proper information about where it came from.
|
||
|
||
#### Scope information
|
||
|
||
UglifyJS contains a scope analyzer that you need to call manually before
|
||
compressing or mangling. Basically it augments various nodes in the AST
|
||
with information about where is a name defined, how many times is a name
|
||
referenced, if it is a global or not, if a function is using `eval` or the
|
||
`with` statement etc. I will discuss this some place else, for now what's
|
||
important to know is that you need to call the following before doing
|
||
anything with the tree:
|
||
```javascript
|
||
toplevel.figure_out_scope()
|
||
```
|
||
|
||
#### Compression
|
||
|
||
Like this:
|
||
```javascript
|
||
var compressor = UglifyJS.Compressor(options);
|
||
var compressed_ast = toplevel.transform(compressor);
|
||
```
|
||
|
||
The `options` can be missing. Available options are discussed above in
|
||
“Compressor options”. Defaults should lead to best compression in most
|
||
scripts.
|
||
|
||
The compressor is destructive, so don't rely that `toplevel` remains the
|
||
original tree.
|
||
|
||
#### Mangling
|
||
|
||
After compression it is a good idea to call again `figure_out_scope` (since
|
||
the compressor might drop unused variables / unreachable code and this might
|
||
change the number of identifiers or their position). Optionally, you can
|
||
call a trick that helps after Gzip (counting character frequency in
|
||
non-mangleable words). Example:
|
||
```javascript
|
||
compressed_ast.figure_out_scope();
|
||
compressed_ast.compute_char_frequency();
|
||
compressed_ast.mangle_names();
|
||
```
|
||
|
||
#### Generating output
|
||
|
||
AST nodes have a `print` method that takes an output stream. Essentially,
|
||
to generate code you do this:
|
||
```javascript
|
||
var stream = UglifyJS.OutputStream(options);
|
||
compressed_ast.print(stream);
|
||
var code = stream.toString(); // this is your minified code
|
||
```
|
||
|
||
or, for a shortcut you can do:
|
||
```javascript
|
||
var code = compressed_ast.print_to_string(options);
|
||
```
|
||
|
||
As usual, `options` is optional. The output stream accepts a lot of options,
|
||
most of them documented above in section “Beautifier options”. The two
|
||
which we care about here are `source_map` and `comments`.
|
||
|
||
#### Keeping comments in the output
|
||
|
||
In order to keep certain comments in the output you need to pass the
|
||
`comments` option. Pass a RegExp or a function. If you pass a RegExp, only
|
||
those comments whose body matches the regexp will be kept. Note that body
|
||
means without the initial `//` or `/*`. If you pass a function, it will be
|
||
called for every comment in the tree and will receive two arguments: the
|
||
node that the comment is attached to, and the comment token itself.
|
||
|
||
The comment token has these properties:
|
||
|
||
- `type`: "comment1" for single-line comments or "comment2" for multi-line
|
||
comments
|
||
- `value`: the comment body
|
||
- `pos` and `endpos`: the start/end positions (zero-based indexes) in the
|
||
original code where this comment appears
|
||
- `line` and `col`: the line and column where this comment appears in the
|
||
original code
|
||
- `file` — the file name of the original file
|
||
- `nlb` — true if there was a newline before this comment in the original
|
||
code, or if this comment contains a newline.
|
||
|
||
Your function should return `true` to keep the comment, or a falsy value
|
||
otherwise.
|
||
|
||
#### Generating a source mapping
|
||
|
||
You need to pass the `source_map` argument when calling `print`. It needs
|
||
to be a `SourceMap` object (which is a thin wrapper on top of the
|
||
[source-map][source-map] library).
|
||
|
||
Example:
|
||
```javascript
|
||
var source_map = UglifyJS.SourceMap(source_map_options);
|
||
var stream = UglifyJS.OutputStream({
|
||
...
|
||
source_map: source_map
|
||
});
|
||
compressed_ast.print(stream);
|
||
|
||
var code = stream.toString();
|
||
var map = source_map.toString(); // json output for your source map
|
||
```
|
||
|
||
The `source_map_options` (optional) can contain the following properties:
|
||
|
||
- `file`: the name of the JavaScript output file that this mapping refers to
|
||
- `root`: the `sourceRoot` property (see the [spec][sm-spec])
|
||
- `orig`: the "original source map", handy when you compress generated JS
|
||
and want to map the minified output back to the original code where it
|
||
came from. It can be simply a string in JSON, or a JSON object containing
|
||
the original source map.
|
||
|
||
[acorn]: https://github.com/ternjs/acorn
|
||
[source-map]: https://github.com/mozilla/source-map
|
||
[sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit
|
||
[codegen]: http://lisperator.net/uglifyjs/codegen
|
||
[compressor]: http://lisperator.net/uglifyjs/compress
|
||
[parser]: http://lisperator.net/uglifyjs/parser
|