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+UglifyJS 3
+==========
+
+UglifyJS is a JavaScript parser, minifier, compressor and beautifier toolkit.
+
+#### Note:
+- **`uglify-js@3` has a simplified [API](#api-reference) and [CLI](#command-line-usage) that is not backwards compatible with [`uglify-js@2`](https://github.com/mishoo/UglifyJS2/tree/v2.x)**.
+- **Documentation for UglifyJS `2.x` releases can be found [here](https://github.com/mishoo/UglifyJS2/tree/v2.x)**.
+- `uglify-js` only supports JavaScript (ECMAScript 5).
+- To minify ECMAScript 2015 or above, transpile using tools like [Babel](https://babeljs.io/).
+
+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
+
+# Command line usage
+
+    uglifyjs [input files] [options]
+
+UglifyJS 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 no input file is specified, UglifyJS will read from STDIN.
+
+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
+
+### Command line options
+
+```
+    -h, --help                  Print usage information.
+                                `--help options` for details on available options.
+    -V, --version               Print version number.
+    -p, --parse <options>       Specify parser options:
+                                `acorn`  Use Acorn for parsing.
+                                `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`.
+                                `expression`  Parse a single expression, rather than
+                                              a program (for parsing JSON).
+                                `spidermonkey`  Assume input files are SpiderMonkey
+                                                AST format (as JSON).
+    -c, --compress [options]    Enable compressor/specify compressor options:
+                                `pure_funcs`  List of functions that can be safely
+                                              removed when their return values are
+                                              not used.
+    -m, --mangle [options]      Mangle names/specify mangler options:
+                                `reserved`  List of names that should not be mangled.
+    --mangle-props [options]    Mangle properties/specify mangler options:
+                                `builtins`  Mangle property names that overlaps
+                                            with standard JavaScript globals.
+                                `debug`  Add debug prefix and suffix.
+                                `domprops`  Mangle property names that overlaps
+                                            with DOM properties.
+                                `keep_quoted`  Only mangle unquoted properties.
+                                `regex`  Only mangle matched property names.
+                                `reserved`  List of names that should not be mangled.
+    -b, --beautify [options]    Beautify output/specify output options:
+                                `beautify`  Enabled with `--beautify` by default.
+                                `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.
+                                `quote_style`  Quote style:
+                                               0 - auto
+                                               1 - single
+                                               2 - double
+                                               3 - original
+                                `wrap_iife`  Wrap IIFEs in parenthesis. Note: you may
+                                             want to disable `negate_iife` under
+                                             compressor options.
+    -o, --output <file>         Output file path (default STDOUT). Specify `ast` or
+                                `spidermonkey` to write UglifyJS or SpiderMonkey AST
+                                as JSON to STDOUT respectively.
+    --comments [filter]         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.
+    --config-file <file>        Read `minify()` options from JSON file.
+    -d, --define <expr>[=value] Global definitions.
+    -e, --enclose [arg[:value]] Embed everything in a big function, with configurable
+                                argument(s) & value(s).
+    --ie8                       Support non-standard Internet Explorer 8.
+                                Equivalent to setting `ie8: true` in `minify()`
+                                for `compress`, `mangle` and `output` options.
+                                By default UglifyJS will not try to be IE-proof.
+    --keep-fnames               Do not mangle/drop function names.  Useful for
+                                code relying on Function.prototype.name.
+    --name-cache <file>         File to hold mangled name mappings.
+    --self                      Build UglifyJS as a library (implies --wrap UglifyJS)
+    --source-map [options]      Enable source map/specify source map options:
+                                `base`  Path to compute relative paths from input files.
+                                `content`  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 within the sources.
+                                `filename`  Filename and/or location of the output source
+                                            (sets `file` attribute in source map).
+                                `includeSources`  Pass this flag if you want to include
+                                                  the content of source files in the
+                                                  source map as sourcesContent property.
+                                `root`  Path to the original source to be included in
+                                        the source map.
+                                `url`  If specified, path to the source map to append in
+                                       `//# sourceMappingURL`.
+    --timings                   Display operations run time on STDERR.
+    --toplevel                  Compress and/or mangle variables in top level scope.
+    --verbose                   Print diagnostic messages.
+    --warn                      Print warning messages.
+    --wrap <name>               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.
+```
+
+Specify `--output` (`-o`) to declare the output file.  Otherwise the output
+goes to STDOUT.
+
+## CLI source map options
+
+UglifyJS can generate a source map file, which is highly useful for
+debugging your compressed JavaScript.  To get a source map, pass
+`--source-map --output output.js` (source map will be written out to
+`output.js.map`).
+
+Additional options:
+
+- `--source-map "filename='<NAME>'"` to specify the name of the source map. The value of
+  `filename` is only used to set `file` attribute (see [the spec][sm-spec])
+  in source map file.
+
+- `--source-map "root='<URL>'"` to pass the URL where the original files can be found.
+
+- `--source-map "url='<URL>'"` to specify the URL where the source map can be found.
+  Otherwise UglifyJS assumes HTTP `X-SourceMap` is being used and will omit the
+  `//# sourceMappingURL=` directive.
+
+For example:
+
+    uglifyjs js/file1.js js/file2.js \
+             -o foo.min.js -c -m \
+             --source-map "root='http://foo.com/src',url='foo.min.js.map'"
+
+The above will compress and mangle `file1.js` and `file2.js`, will drop the
+output in `foo.min.js` and the source map in `foo.min.js.map`.  The source
+mapping will refer to `http://foo.com/src/js/file1.js` and
+`http://foo.com/src/js/file2.js` (in fact it will list `http://foo.com/src`
+as the source map root, and the original files as `js/file1.js` and
+`js/file2.js`).
+
+### Composed source map
+
+When you're compressing JS code that was output by a compiler such as
+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
+CoffeeScript → compiled JS, UglifyJS can generate a map from CoffeeScript →
+compressed JS by mapping every token in the compiled JS to its original
+location.
+
+To use this feature pass `--source-map "content='/path/to/input/source.map'"`
+or `--source-map "content=inline"` if the source map is included inline with
+the sources.
+
+## CLI compress options
+
+You need to pass `--compress` (`-c`) to enable the compressor.  Optionally
+you can pass a comma-separated list of [compress options](#compress-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`).
+
+Example:
+
+    uglifyjs file.js -c toplevel,sequences=false
+
+## CLI mangle options
+
+To enable the mangler you need to pass `--mangle` (`-m`).  The following
+(comma-separated) options are supported:
+
+- `toplevel` (default `false`) -- mangle names declared in the top level scope.
+
+- `eval` (default `false`) -- mangle names visible in scopes where `eval` or `with` are used.
+
+When mangling is enabled but you want to prevent certain names from being
+mangled, you can declare those names with `--mangle reserved` — pass a
+comma-separated list of names.  For example:
+
+    uglifyjs ... -m reserved=['$','require','exports']
+
+to prevent the `require`, `exports` and `$` names from being changed.
+
+### CLI mangling property names (`--mangle-props`)
+
+**Note:** THIS WILL PROBABLY BREAK YOUR CODE.  Mangling property names
+is a separate step, different from variable name mangling.  Pass
+`--mangle-props` to enable it.  It will mangle all properties in the
+input code with the exception of built in DOM properties and properties
+in core JavaScript classes.  For example:
+
+```javascript
+// example.js
+var x = {
+    baz_: 0,
+    foo_: 1,
+    calc: function() {
+        return this.foo_ + this.baz_;
+    }
+};
+x.bar_ = 2;
+x["baz_"] = 3;
+console.log(x.calc());
+```
+Mangle all properties (except for JavaScript `builtins`):
+```bash
+$ uglifyjs example.js -c -m --mangle-props
+```
+```javascript
+var x={o:0,_:1,l:function(){return this._+this.o}};x.t=2,x.o=3,console.log(x.l());
+```
+Mangle all properties except for `reserved` properties:
+```bash
+$ uglifyjs example.js -c -m --mangle-props reserved=[foo_,bar_]
+```
+```javascript
+var x={o:0,foo_:1,_:function(){return this.foo_+this.o}};x.bar_=2,x.o=3,console.log(x._());
+```
+Mangle all properties matching a `regex`:
+```bash
+$ uglifyjs example.js -c -m --mangle-props regex=/_$/
+```
+```javascript
+var x={o:0,_:1,calc:function(){return this._+this.o}};x.l=2,x.o=3,console.log(x.calc());
+```
+
+Combining mangle properties options:
+```bash
+$ uglifyjs example.js -c -m --mangle-props regex=/_$/,reserved=[bar_]
+```
+```javascript
+var x={o:0,_:1,calc:function(){return this._+this.o}};x.bar_=2,x.o=3,console.log(x.calc());
+```
+
+In order for this to be of any use, we avoid mangling standard JS names by
+default (`--mangle-props builtins` to override).
+
+A default exclusion file is provided in `tools/domprops.json` which should
+cover most standard JS and DOM properties defined in various browsers.  Pass
+`--mangle-props domprops` to disable this feature.
+
+A regular expression can be used to define which property names should be
+mangled.  For example, `--mangle-props regex=/^_/` will only mangle property
+names that start with an underscore.
+
+When you compress multiple files using this option, in order for them to
+work together in the end we need to ensure somehow that one property gets
+mangled to the same name in all of them.  For this, pass `--name-cache filename.json`
+and UglifyJS will maintain these mappings in a file which can then be reused.
+It should be initially empty.  Example:
+
+```bash
+$ 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.
+
+### Mangling unquoted names (`--mangle-props keep_quoted`)
+
+Using quoted property name (`o["foo"]`) reserves the property name (`foo`)
+so that it is not mangled throughout the entire script even when used in an
+unquoted style (`o.foo`). Example:
+
+```javascript
+// stuff.js
+var o = {
+    "foo": 1,
+    bar: 3
+};
+o.foo += o.bar;
+console.log(o.foo);
+```
+```bash
+$ uglifyjs stuff.js --mangle-props keep_quoted -c -m
+```
+```javascript
+var o={foo:1,o:3};o.foo+=o.o,console.log(o.foo);
+```
+
+### Debugging property name mangling
+
+You can also pass `--mangle-props debug` in order to mangle property names
+without completely obscuring them. For example the property `o.foo`
+would mangle to `o._$foo$_` with this option. This allows property mangling
+of a large codebase while still being able to debug the code and identify
+where mangling is breaking things.
+
+```bash
+$ uglifyjs stuff.js --mangle-props debug -c -m
+```
+```javascript
+var o={_$foo$_:1,_$bar$_:3};o._$foo$_+=o._$bar$_,console.log(o._$foo$_);
+```
+
+You can also pass a custom suffix using `--mangle-props debug=XYZ`. This would then
+mangle `o.foo` to `o._$foo$XYZ_`. You can change this each time you compile a
+script to identify how a property got mangled. One technique is to pass a
+random number on every compile to simulate mangling changing with different
+inputs (e.g. as you update the input script with new properties), and to help
+identify mistakes like writing mangled keys to storage.
+
+
+# API Reference
+
+Assuming installation via NPM, you can load UglifyJS in your application
+like this:
+```javascript
+var UglifyJS = require("uglify-js");
+```
+
+There is a single high level function, **`minify(code, options)`**,
+which will perform all minification [phases](#minify-options) in a configurable
+manner. By default `minify()` will enable the options [`compress`](#compress-options)
+and [`mangle`](#mangle-options). Example:
+```javascript
+var code = "function add(first, second) { return first + second; }";
+var result = UglifyJS.minify(code);
+console.log(result.error); // runtime error, or `undefined` if no error
+console.log(result.code);  // minified output: function add(n,d){return n+d}
+```
+
+You can `minify` more than one JavaScript file at a time by using an object
+for the first argument where the keys are file names and the values are source
+code:
+```javascript
+var code = {
+    "file1.js": "function add(first, second) { return first + second; }",
+    "file2.js": "console.log(add(1 + 2, 3 + 4));"
+};
+var result = UglifyJS.minify(code);
+console.log(result.code);
+// function add(d,n){return d+n}console.log(add(3,7));
+```
+
+The `toplevel` option:
+```javascript
+var code = {
+    "file1.js": "function add(first, second) { return first + second; }",
+    "file2.js": "console.log(add(1 + 2, 3 + 4));"
+};
+var options = { toplevel: true };
+var result = UglifyJS.minify(code, options);
+console.log(result.code);
+// console.log(3+7);
+```
+
+The `nameCache` option:
+```javascript
+var options = {
+    mangle: {
+        toplevel: true,
+    },
+    nameCache: {}
+};
+var result1 = UglifyJS.minify({
+    "file1.js": "function add(first, second) { return first + second; }"
+}, options);
+var result2 = UglifyJS.minify({
+    "file2.js": "console.log(add(1 + 2, 3 + 4));"
+}, options);
+console.log(result1.code);
+// function n(n,r){return n+r}
+console.log(result2.code);
+// console.log(n(3,7));
+```
+
+You may persist the name cache to the file system in the following way:
+```javascript
+var cacheFileName = "/tmp/cache.json";
+var options = {
+    mangle: {
+        properties: true,
+    },
+    nameCache: JSON.parse(fs.readFileSync(cacheFileName, "utf8"))
+};
+fs.writeFileSync("part1.js", UglifyJS.minify({
+    "file1.js": fs.readFileSync("file1.js", "utf8"),
+    "file2.js": fs.readFileSync("file2.js", "utf8")
+}, options).code, "utf8");
+fs.writeFileSync("part2.js", UglifyJS.minify({
+    "file3.js": fs.readFileSync("file3.js", "utf8"),
+    "file4.js": fs.readFileSync("file4.js", "utf8")
+}, options).code, "utf8");
+fs.writeFileSync(cacheFileName, JSON.stringify(options.nameCache), "utf8");
+```
+
+An example of a combination of `minify()` options:
+```javascript
+var code = {
+    "file1.js": "function add(first, second) { return first + second; }",
+    "file2.js": "console.log(add(1 + 2, 3 + 4));"
+};
+var options = {
+    toplevel: true,
+    compress: {
+        global_defs: {
+            "@console.log": "alert"
+        },
+        passes: 2
+    },
+    output: {
+        beautify: false,
+        preamble: "/* uglified */"
+    }
+};
+var result = UglifyJS.minify(code, options);
+console.log(result.code);
+// /* uglified */
+// alert(10);"
+```
+
+To produce warnings:
+```javascript
+var code = "function f(){ var u; return 2 + 3; }";
+var options = { warnings: true };
+var result = UglifyJS.minify(code, options);
+console.log(result.error);    // runtime error, `undefined` in this case
+console.log(result.warnings); // [ 'Dropping unused variable u [0:1,18]' ]
+console.log(result.code);     // function f(){return 5}
+```
+
+An error example:
+```javascript
+var result = UglifyJS.minify({"foo.js" : "if (0) else console.log(1);"});
+console.log(JSON.stringify(result.error));
+// {"message":"Unexpected token: keyword (else)","filename":"foo.js","line":1,"col":7,"pos":7}
+```
+Note: unlike `uglify-js@2.x`, the `3.x` API does not throw errors. To
+achieve a similar effect one could do the following:
+```javascript
+var result = UglifyJS.minify(code, options);
+if (result.error) throw result.error;
+```
+
+## Minify options
+
+- `warnings` (default `false`) — pass `true` to return compressor warnings
+  in `result.warnings`. Use the value `"verbose"` for more detailed warnings.
+
+- `parse` (default `{}`) — pass an object if you wish to specify some
+  additional [parse options](#parse-options).
+
+- `compress` (default `{}`) — pass `false` to skip compressing entirely.
+  Pass an object to specify custom [compress options](#compress-options).
+
+- `mangle` (default `true`) — pass `false` to skip mangling names, or pass
+  an object to specify [mangle options](#mangle-options) (see below).
+
+  - `mangle.properties` (default `false`) — a subcategory of the mangle option.
+    Pass an object to specify custom [mangle property options](#mangle-properties-options).
+
+- `output` (default `null`) — pass an object if you wish to specify
+  additional [output options](#output-options).  The defaults are optimized
+  for best compression.
+
+- `sourceMap` (default `false`) - pass an object if you wish to specify
+  [source map options](#source-map-options).
+
+- `toplevel` (default `false`) - set to `true` if you wish to enable top level
+  variable and function name mangling and to drop unused variables and functions.
+
+- `nameCache` (default `null`) - pass an empty object `{}` or a previously
+  used `nameCache` object if you wish to cache mangled variable and
+  property names across multiple invocations of `minify()`. Note: this is
+  a read/write property. `minify()` will read the name cache state of this
+  object and update it during minification so that it may be
+  reused or externally persisted by the user.
+
+- `ie8` (default `false`) - set to `true` to support IE8.
+
+- `keep_fnames` (default: `false`) - pass `true` to prevent discarding or mangling
+  of function names.  Useful for code relying on `Function.prototype.name`.
+
+## Minify options structure
+
+```javascript
+{
+    parse: {
+        // parse options
+    },
+    compress: {
+        // compress options
+    },
+    mangle: {
+        // mangle options
+
+        properties: {
+            // mangle property options
+        }
+    },
+    output: {
+        // output options
+    },
+    sourceMap: {
+        // source map options
+    },
+    nameCache: null, // or specify a name cache object
+    toplevel: false,
+    ie8: false,
+    warnings: false,
+}
+```
+
+### Source map options
+
+To generate a source map:
+```javascript
+var result = UglifyJS.minify({"file1.js": "var a = function() {};"}, {
+    sourceMap: {
+        filename: "out.js",
+        url: "out.js.map"
+    }
+});
+console.log(result.code); // minified output
+console.log(result.map);  // source map
+```
+
+Note that the source map is not saved in a file, it's just returned in
+`result.map`.  The value passed for `sourceMap.url` is only used to set
+`//# sourceMappingURL=out.js.map` in `result.code`. The value of
+`filename` is only used to set `file` attribute (see [the spec][sm-spec])
+in source map file.
+
+You can set option `sourceMap.url` to be `"inline"` and source map will
+be appended to code.
+
+You can also specify sourceRoot property to be included in source map:
+```javascript
+var result = UglifyJS.minify({"file1.js": "var a = function() {};"}, {
+    sourceMap: {
+        root: "http://example.com/src",
+        url: "out.js.map"
+    }
+});
+```
+
+If you're compressing compiled JavaScript and have a source map for it, you
+can use `sourceMap.content`:
+```javascript
+var result = UglifyJS.minify({"compiled.js": "compiled code"}, {
+    sourceMap: {
+        content: "content from compiled.js.map",
+        url: "minified.js.map"
+    }
+});
+// same as before, it returns `code` and `map`
+```
+
+If you're using the `X-SourceMap` header instead, you can just omit `sourceMap.url`.
+
+## Parse options
+
+- `bare_returns` (default `false`) -- support top level `return` statements
+
+- `html5_comments` (default `true`)
+
+- `shebang` (default `true`) -- support `#!command` as the first line
+
+## Compress options
+
+- `arguments` (default: `true`) -- replace `arguments[index]` with function
+  parameter name whenever possible.
+
+- `booleans` (default: `true`) -- various optimizations for boolean context,
+  for example `!!a ? b : c → a ? b : c`
+
+- `collapse_vars` (default: `true`) -- Collapse single-use non-constant variables,
+  side effects permitting.
+
+- `comparisons` (default: `true`) -- apply certain optimizations to binary nodes,
+  e.g. `!(a <= b) → a > b`, attempts to negate binary nodes, e.g.
+  `a = !b && !c && !d && !e → a=!(b||c||d||e)` etc.
+
+- `conditionals` (default: `true`) -- apply optimizations for `if`-s and conditional
+  expressions
+
+- `dead_code` (default: `true`) -- remove unreachable code
+
+- `directives` (default: `true`) -- remove redundant or non-standard directives
+
+- `drop_console` (default: `false`) -- Pass `true` to discard calls to
+  `console.*` functions. If you wish to drop a specific function call
+  such as `console.info` and/or retain side effects from function arguments
+  after dropping the function call then use `pure_funcs` instead.
+
+- `drop_debugger` (default: `true`) -- remove `debugger;` statements
+
+- `evaluate` (default: `true`) -- attempt to evaluate constant expressions
+
+- `expression` (default: `false`) -- Pass `true` to preserve completion values
+  from terminal statements without `return`, e.g. in bookmarklets.
+
+- `global_defs` (default: `{}`) -- see [conditional compilation](#conditional-compilation)
+
+- `hoist_funs` (default: `false`) -- hoist function declarations
+
+- `hoist_props` (default: `true`) -- hoist properties from constant object and
+  array literals into regular variables subject to a set of constraints. For example:
+  `var o={p:1, q:2}; f(o.p, o.q);` is converted to `f(1, 2);`. Note: `hoist_props`
+  works best with `mangle` enabled, the `compress` option `passes` set to `2` or higher,
+  and the `compress` option `toplevel` enabled.
+
+- `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` (default: `true`) -- optimizations for if/return and if/continue
+
+- `inline` (default: `true`) -- inline calls to function with simple/`return` statement:
+  - `false` -- same as `0`
+  - `0` -- disabled inlining
+  - `1` -- inline simple functions
+  - `2` -- inline functions with arguments
+  - `3` -- inline functions with arguments and variables
+  - `true` -- same as `3`
+
+- `join_vars` (default: `true`) -- join consecutive `var` statements
+
+- `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 discarding function names.  Useful for code relying on
+  `Function.prototype.name`. See also: the `keep_fnames` [mangle option](#mangle).
+
+- `keep_infinity` (default: `false`) -- Pass `true` to prevent `Infinity` from
+  being compressed into `1/0`, which may cause performance issues on Chrome.
+
+- `loops` (default: `true`) -- optimizations for `do`, `while` and `for` loops
+  when we can statically determine the condition.
+
+- `negate_iife` (default: `true`) -- negate "Immediately-Called Function Expressions"
+  where the return value is discarded, to avoid the parens that the
+  code generator would insert.
+
+- `passes` (default: `1`) -- The maximum number of times to run compress.
+  In some cases more than one pass leads to further compressed code.  Keep in
+  mind more passes will take more time.
+
+- `properties` (default: `true`) -- rewrite property access using the dot notation, for
+  example `foo["bar"] → foo.bar`
+
+- `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). Make sure symbols under `pure_funcs`
+  are also under `mangle.reserved` to avoid mangling.
+
+- `pure_getters` (default: `"strict"`) -- 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.
+  Specify `"strict"` to treat `foo.bar` as side-effect-free only when
+  `foo` is certain to not throw, i.e. not `null` or `undefined`.
+
+- `reduce_funcs` (default: `true`) -- Allows single-use functions to be
+  inlined as function expressions when permissible allowing further
+  optimization.  Enabled by default.  Option depends on `reduce_vars`
+  being enabled.  Some code runs faster in the Chrome V8 engine if this
+  option is disabled.  Does not negatively impact other major browsers.
+
+- `reduce_vars` (default: `true`) -- Improve optimization on variables assigned with and
+  used as constant values.
+
+- `sequences` (default: `true`) -- join consecutive simple statements using the
+  comma operator.  May be set to a positive integer to specify the maximum number
+  of consecutive comma sequences that will be generated. If this option is set to
+  `true` then the default `sequences` limit is `200`. Set option to `false` or `0`
+  to disable. The smallest `sequences` length is `2`. A `sequences` value of `1`
+  is grandfathered to be equivalent to `true` and as such means `200`. On rare
+  occasions the default sequences limit leads to very slow compress times in which
+  case a value of `20` or less is recommended.
+
+- `side_effects` (default: `true`) -- Pass `false` to disable potentially dropping
+  functions marked as "pure".  A function call is marked as "pure" if a comment
+  annotation `/*@__PURE__*/` or `/*#__PURE__*/` immediately precedes the call. For
+  example: `/*@__PURE__*/foo();`
+
+- `switches` (default: `true`) -- de-duplicate and remove unreachable `switch` branches
+
+- `toplevel` (default: `false`) -- drop unreferenced functions (`"funcs"`) and/or
+  variables (`"vars"`) in the top level scope (`false` by default, `true` to drop
+  both unreferenced functions and variables)
+
+- `top_retain` (default: `null`) -- prevent specific toplevel functions and
+  variables from `unused` removal (can be array, comma-separated, RegExp or
+  function. Implies `toplevel`)
+
+- `typeofs` (default: `true`) -- Transforms `typeof foo == "undefined"` into
+  `foo === void 0`.  Note: recommend to set this value to `false` for IE10 and
+  earlier versions due to known issues.
+
+- `unsafe` (default: `false`) -- apply "unsafe" transformations (discussion below)
+
+- `unsafe_comps` (default: `false`) -- compress expressions like `a <= b` assuming
+  none of the operands can be (coerced to) `NaN`.
+
+- `unsafe_Function` (default: `false`) -- compress and mangle `Function(args, code)`
+  when both `args` and `code` are string literals.
+
+- `unsafe_math` (default: `false`) -- optimize numerical expressions like
+  `2 * x * 3` into `6 * x`, which may give imprecise floating point results.
+
+- `unsafe_proto` (default: `false`) -- optimize expressions like
+  `Array.prototype.slice.call(a)` into `[].slice.call(a)`
+
+- `unsafe_regexp` (default: `false`) -- enable substitutions of variables with
+  `RegExp` values the same way as if they are constants.
+
+- `unsafe_undefined` (default: `false`) -- substitute `void 0` if there is a
+  variable named `undefined` in scope (variable name will be mangled, typically
+  reduced to a single character)
+
+- `unused` (default: `true`) -- drop unreferenced functions and variables (simple
+  direct variable assignments do not count as references unless set to `"keep_assign"`)
+
+- `warnings` (default: `false`) -- display warnings when dropping unreachable
+  code or unused declarations etc.
+
+## Mangle options
+
+- `eval` (default `false`) -- Pass `true` to mangle names visible in scopes
+  where `eval` or `with` are used.
+
+- `keep_fnames` (default `false`) -- Pass `true` to not mangle function names.
+  Useful for code relying on `Function.prototype.name`. See also: the `keep_fnames`
+  [compress option](#compress-options).
+
+- `reserved` (default `[]`) -- Pass an array of identifiers that should be
+  excluded from mangling. Example: `["foo", "bar"]`.
+
+- `toplevel` (default `false`) -- Pass `true` to mangle names declared in the
+  top level scope.
+
+Examples:
+
+```javascript
+// test.js
+var globalVar;
+function funcName(firstLongName, anotherLongName) {
+    var myVariable = firstLongName +  anotherLongName;
+}
+```
+```javascript
+var code = fs.readFileSync("test.js", "utf8");
+
+UglifyJS.minify(code).code;
+// 'function funcName(a,n){}var globalVar;'
+
+UglifyJS.minify(code, { mangle: { reserved: ['firstLongName'] } }).code;
+// 'function funcName(firstLongName,a){}var globalVar;'
+
+UglifyJS.minify(code, { mangle: { toplevel: true } }).code;
+// 'function n(n,a){}var a;'
+```
+
+### Mangle properties options
+
+- `builtins` (default: `false`) -- Use `true` to allow the mangling of builtin
+  DOM properties. Not recommended to override this setting.
+
+- `debug` (default: `false`) -— Mangle names with the original name still present.
+  Pass an empty string `""` to enable, or a non-empty string to set the debug suffix.
+
+- `keep_quoted` (default: `false`) -— Only mangle unquoted property names.
+
+- `regex` (default: `null`) -— Pass a RegExp literal to only mangle property
+  names matching the regular expression.
+
+- `reserved` (default: `[]`) -- Do not mangle property names listed in the
+  `reserved` array.
+
+## Output 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:
+
+- `ascii_only` (default `false`) -- escape Unicode characters in strings and
+  regexps (affects directives with non-ascii characters becoming invalid)
+
+- `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.
+
+- `braces` (default `false`) -- always insert braces in `if`, `for`,
+  `do`, `while` or `with` statements, even if their body is a single
+  statement.
+
+- `comments` (default `false`) -- pass `true` or `"all"` to preserve all
+  comments, `"some"` to preserve some comments, a regular expression string
+  (e.g. `/^!/`) or a function.
+
+- `indent_level` (default `4`)
+
+- `indent_start` (default `0`) -- prefix all lines by that many spaces
+
+- `inline_script` (default `true`) -- escape HTML comments and the slash in
+  occurrences of `</script>` in strings
+
+- `keep_quoted_props` (default `false`) -- when turned on, prevents stripping
+  quotes from property names in object literals.
+
+- `max_line_len` (default `false`) -- maximum line length (for uglified code)
+
+- `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.
+
+- `preserve_line` (default `false`) -- pass `true` to retain line numbering on
+  a best effort basis.
+
+- `quote_keys` (default `false`) -- pass `true` to quote all keys in literal
+  objects
+
+- `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. `0` is best for gzip size.
+  - `1` -- always use single quotes
+  - `2` -- always use double quotes
+  - `3` -- always use the original quotes
+
+- `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).
+
+- `shebang` (default `true`) -- preserve shebang `#!` in preamble (bash scripts)
+
+- `webkit` (default `false`) -- enable workarounds for WebKit bugs.
+  PhantomJS users should set this option to `true`.
+
+- `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.
+
+- `wrap_iife` (default `false`) -- pass `true` to wrap immediately invoked
+  function expressions. See
+  [#640](https://github.com/mishoo/UglifyJS2/issues/640) for more details.
+
+# Miscellaneous
+
+### 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 /^!/`
+will keep comments like `/*! Copyright Notice */`.
+
+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.
+
+### The `unsafe` `compress` 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`
+
+### 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");
+}
+```
+
+You can specify nested constants in the form of `--define env.DEBUG=false`.
+
+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
+var DEBUG = false;
+var PRODUCTION = true;
+// 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 which does not support `const`,
+using `var` with `reduce_vars` (enabled by default) should suffice.
+
+### 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:
+
+```javascript
+var result = UglifyJS.minify(fs.readFileSync("input.js", "utf8"), {
+    compress: {
+        dead_code: true,
+        global_defs: {
+            DEBUG: false
+        }
+    }
+});
+```
+
+To replace an identifier with an arbitrary non-constant expression it is
+necessary to prefix the `global_defs` key with `"@"` to instruct UglifyJS
+to parse the value as an expression:
+```javascript
+UglifyJS.minify("alert('hello');", {
+    compress: {
+        global_defs: {
+            "@alert": "console.log"
+        }
+    }
+}).code;
+// returns: 'console.log("hello");'
+```
+
+Otherwise it would be replaced as string literal:
+```javascript
+UglifyJS.minify("alert('hello');", {
+    compress: {
+        global_defs: {
+            "alert": "console.log"
+        }
+    }
+}).code;
+// returns: '"console.log"("hello");'
+```
+
+### Using native Uglify AST with `minify()`
+```javascript
+// example: parse only, produce native Uglify AST
+
+var result = UglifyJS.minify(code, {
+    parse: {},
+    compress: false,
+    mangle: false,
+    output: {
+        ast: true,
+        code: false  // optional - faster if false
+    }
+});
+
+// result.ast contains native Uglify AST
+```
+```javascript
+// example: accept native Uglify AST input and then compress and mangle
+//          to produce both code and native AST.
+
+var result = UglifyJS.minify(ast, {
+    compress: {},
+    mangle: {},
+    output: {
+        ast: true,
+        code: true  // optional - faster if false
+    }
+});
+
+// result.ast contains native Uglify AST
+// result.code contains the minified code in string form.
+```
+
+### Working with Uglify AST
+
+Transversal and transformation of the native AST can be performed through
+[`TreeWalker`](https://github.com/mishoo/UglifyJS2/blob/master/lib/ast.js) and
+[`TreeTransformer`](https://github.com/mishoo/UglifyJS2/blob/master/lib/transform.js)
+respectively.
+
+### ESTree / SpiderMonkey AST
+
+UglifyJS 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 -p spidermonkey -m -c
+
+The `-p 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 `-p 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.
+
+[acorn]: https://github.com/ternjs/acorn
+[sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k
+
+### Uglify Fast Minify Mode
+
+It's not well known, but whitespace removal and symbol mangling accounts
+for 95% of the size reduction in minified code for most JavaScript - not
+elaborate code transforms. One can simply disable `compress` to speed up
+Uglify builds by 3 to 4 times. In this fast `mangle`-only mode Uglify has
+comparable minify speeds and gzip sizes to
+[`butternut`](https://www.npmjs.com/package/butternut):
+
+| d3.js | minify size | gzip size | minify time (seconds) |
+| --- | ---: | ---: | ---: |
+| original | 451,131 | 108,733 | - |
+| uglify-js@3.0.24 mangle=false, compress=false | 316,600 | 85,245 | 0.70 |
+| uglify-js@3.0.24 mangle=true, compress=false | 220,216 | 72,730 | 1.13 |
+| butternut@0.4.6 | 217,568 | 72,738 | 1.41 |
+| uglify-js@3.0.24 mangle=true, compress=true | 212,511 | 71,560 | 3.36 |
+| babili@0.1.4 | 210,713 | 72,140 | 12.64 |
+
+To enable fast minify mode from the CLI use:
+```
+uglifyjs file.js -m
+```
+To enable fast minify mode with the API use:
+```js
+UglifyJS.minify(code, { compress: false, mangle: true });
+```
+
+#### Source maps and debugging
+
+Various `compress` transforms that simplify, rearrange, inline and remove code
+are known to have an adverse effect on debugging with source maps. This is
+expected as code is optimized and mappings are often simply not possible as
+some code no longer exists. For highest fidelity in source map debugging
+disable the Uglify `compress` option and just use `mangle`.
+
+### Compiler assumptions
+
+To allow for better optimizations, the compiler makes various assumptions:
+
+- `.toString()` and `.valueOf()` don't have side effects, and for built-in
+  objects they have not been overridden.
+- `undefined`, `NaN` and `Infinity` have not been externally redefined.
+- `arguments.callee`, `arguments.caller` and `Function.prototype.caller` are not used.
+- The code doesn't expect the contents of `Function.prototype.toString()` or
+  `Error.prototype.stack` to be anything in particular.
+- Getting and setting properties on a plain object does not cause other side effects
+  (using `.watch()` or `Proxy`).
+- Object properties can be added, removed and modified (not prevented with
+  `Object.defineProperty()`, `Object.defineProperties()`, `Object.freeze()`,
+  `Object.preventExtensions()` or `Object.seal()`).