summaryrefslogtreecommitdiffstats
path: root/node_modules/terser/README.md
diff options
context:
space:
mode:
Diffstat (limited to 'node_modules/terser/README.md')
-rw-r--r--node_modules/terser/README.md1390
1 files changed, 0 insertions, 1390 deletions
diff --git a/node_modules/terser/README.md b/node_modules/terser/README.md
deleted file mode 100644
index a69dfa4..0000000
--- a/node_modules/terser/README.md
+++ /dev/null
@@ -1,1390 +0,0 @@
-<h1><img src="https://terser.org/img/terser-banner-logo.png" alt="Terser" width="400"></h1>
-
- [![NPM Version][npm-image]][npm-url]
- [![NPM Downloads][downloads-image]][downloads-url]
- [![Travis Build][travis-image]][travis-url]
- [![Opencollective financial contributors][opencollective-contributors]][opencollective-url]
-
-A JavaScript parser and mangler/compressor toolkit for ES6+.
-
-*note*: You can support this project on patreon: <a target="_blank" rel="nofollow" href="https://www.patreon.com/fabiosantoscode"><img src="https://c5.patreon.com/external/logo/become_a_patron_button@2x.png" alt="patron" width="100px" height="auto"></a>. Check out [PATRONS.md](https://github.com/terser/terser/blob/master/PATRONS.md) for our first-tier patrons.
-
-Terser recommends you use RollupJS to bundle your modules, as that produces smaller code overall.
-
-*Beautification* has been undocumented and is *being removed* from terser, we recommend you use [prettier](https://npmjs.com/package/prettier).
-
-Find the changelog in [CHANGELOG.md](https://github.com/terser/terser/blob/master/CHANGELOG.md)
-
-
-
-[npm-image]: https://img.shields.io/npm/v/terser.svg
-[npm-url]: https://npmjs.org/package/terser
-[downloads-image]: https://img.shields.io/npm/dm/terser.svg
-[downloads-url]: https://npmjs.org/package/terser
-[travis-image]: https://img.shields.io/travis/terser/terser/master.svg
-[travis-url]: https://travis-ci.org/terser/terser
-[opencollective-contributors]: https://opencollective.com/terser/tiers/badge.svg
-[opencollective-url]: https://opencollective.com/terser
-
-Why choose terser?
-------------------
-
-`uglify-es` is [no longer maintained](https://github.com/mishoo/UglifyJS2/issues/3156#issuecomment-392943058) and `uglify-js` does not support ES6+.
-
-**`terser`** is a fork of `uglify-es` that mostly retains API and CLI compatibility
-with `uglify-es` and `uglify-js@3`.
-
-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 terser -g
-
-From NPM for programmatic use:
-
- npm install terser
-
-# Command line usage
-
- terser [input files] [options]
-
-Terser can take multiple input files. It's recommended that you pass the
-input files first, then pass the options. Terser 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, Terser 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:
-
- terser --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 and DOM
- API props.
- `debug` Add debug prefix and suffix.
- `keep_quoted` Only mangle unquoted properties, quoted
- properties are automatically reserved.
- `strict` disables quoted properties
- being automatically reserved.
- `regex` Only mangle matched property names.
- `reserved` List of names that should not be mangled.
- -b, --beautify [options] Specify output options:
- `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.
- `wrap_func_args` Wrap function arguments in parenthesis.
- -o, --output <file> Output file path (default STDOUT). Specify `ast` or
- `spidermonkey` to write Terser 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
- - `false` to omit comments in the output
- - 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.
- --ecma <version> Specify ECMAScript release: 5, 2015, 2016, etc.
- -e, --enclose [arg[:value]] Embed output in a big function with configurable
- arguments and values.
- --ie8 Support non-standard Internet Explorer 8.
- Equivalent to setting `ie8: true` in `minify()`
- for `compress`, `mangle` and `output` options.
- By default Terser will not try to be IE-proof.
- --keep-classnames Do not mangle/drop class names.
- --keep-fnames Do not mangle/drop function names. Useful for
- code relying on Function.prototype.name.
- --module Input is an ES6 module. If `compress` or `mangle` is
- enabled then the `toplevel` option will be enabled.
- --name-cache <file> File to hold mangled name mappings.
- --safari10 Support non-standard Safari 10/11.
- Equivalent to setting `safari10: true` in `minify()`
- for `mangle` and `output` options.
- By default `terser` will not work around
- Safari 10/11 bugs.
- --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` Name and/or location of the output source.
- `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
-
-Terser 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.
-
-- `--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 Terser assumes HTTP `X-SourceMap` is being used and will omit the
- `//# sourceMappingURL=` directive.
-
-For example:
-
- terser 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). Terser has an
-option to take an input source map. Assuming you have a mapping from
-CoffeeScript → compiled JS, Terser 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:
-
- terser 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:
-
- terser ... -m reserved=['$','require','exports']
-
-to prevent the `require`, `exports` and `$` names from being changed.
-
-### CLI mangling property names (`--mangle-props`)
-
-**Note:** THIS **WILL** BREAK YOUR CODE. A good rule of thumb is not to use this unless you know exactly what you're doing and how this works and read this section until the end.
-
-Mangling property names is a separate step, different from variable name mangling. Pass
-`--mangle-props` to enable it. The least dangerous
-way to use this is to use the `regex` option like so:
-
-```
-terser example.js -c -m --mangle-props regex=/_$/
-```
-
-This will mangle all properties that end with an
-underscore. So you can use it to mangle internal methods.
-
-By default, it will mangle all properties in the
-input code with the exception of built in DOM properties and properties
-in core JavaScript classes, which is what will break your code if you don't:
-
-1. Control all the code you're mangling
-2. Avoid using a module bundler, as they usually will call Terser on each file individually, making it impossible to pass mangled objects between modules.
-3. Avoid calling functions like `defineProperty` or `hasOwnProperty`, because they refer to object properties using strings and will break your code if you don't know what you are doing.
-
-An example:
-
-```javascript
-// example.js
-var x = {
- baz_: 0,
- foo_: 1,
- calc: function() {
- return this.foo_ + this.baz_;
- }
-};
-x.bar_ = 2;
-x["baz_"] = 3;
-console.log(x.calc());
-```
-Mangle all properties (except for JavaScript `builtins`) (**very** unsafe):
-```bash
-$ terser example.js -c passes=2 -m --mangle-props
-```
-```javascript
-var x={o:3,t:1,i:function(){return this.t+this.o},s:2};console.log(x.i());
-```
-Mangle all properties except for `reserved` properties (still very unsafe):
-```bash
-$ terser example.js -c passes=2 -m --mangle-props reserved=[foo_,bar_]
-```
-```javascript
-var x={o:3,foo_:1,t:function(){return this.foo_+this.o},bar_:2};console.log(x.t());
-```
-Mangle all properties matching a `regex` (not as unsafe but still unsafe):
-```bash
-$ terser example.js -c passes=2 -m --mangle-props regex=/_$/
-```
-```javascript
-var x={o:3,t:1,calc:function(){return this.t+this.o},i:2};console.log(x.calc());
-```
-
-Combining mangle properties options:
-```bash
-$ terser example.js -c passes=2 -m --mangle-props regex=/_$/,reserved=[bar_]
-```
-```javascript
-var x={o:3,t:1,calc:function(){return this.t+this.o},bar_:2};console.log(x.calc());
-```
-
-In order for this to be of any use, we avoid mangling standard JS names and DOM
-API properties by default (`--mangle-props builtins` to override).
-
-A regular expression can be used to define which property names should be
-mangled. For example, `--mangle-props regex=/^_/` will only mangle property
-names that start with an underscore.
-
-When you compress multiple files using this option, in order for them to
-work together in the end we need to ensure somehow that one property gets
-mangled to the same name in all of them. For this, pass `--name-cache filename.json`
-and Terser will maintain these mappings in a file which can then be reused.
-It should be initially empty. Example:
-
-```bash
-$ rm -f /tmp/cache.json # start fresh
-$ terser file1.js file2.js --mangle-props --name-cache /tmp/cache.json -o part1.js
-$ terser 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 Terser.
-
-### 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
-$ terser 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
-$ terser 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 Terser in your application
-like this:
-```javascript
-var Terser = require("terser");
-```
-Browser loading is also supported:
-```html
-<script src="node_modules/source-map/dist/source-map.min.js"></script>
-<script src="dist/bundle.min.js"></script>
-```
-
-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 = Terser.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 = Terser.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 = Terser.minify(code, options);
-console.log(result.code);
-// console.log(3+7);
-```
-
-The `nameCache` option:
-```javascript
-var options = {
- mangle: {
- toplevel: true,
- },
- nameCache: {}
-};
-var result1 = Terser.minify({
- "file1.js": "function add(first, second) { return first + second; }"
-}, options);
-var result2 = Terser.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", Terser.minify({
- "file1.js": fs.readFileSync("file1.js", "utf8"),
- "file2.js": fs.readFileSync("file2.js", "utf8")
-}, options).code, "utf8");
-fs.writeFileSync("part2.js", Terser.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: "/* minified */"
- }
-};
-var result = Terser.minify(code, options);
-console.log(result.code);
-// /* minified */
-// alert(10);"
-```
-
-To produce warnings:
-```javascript
-var code = "function f(){ var u; return 2 + 3; }";
-var options = { warnings: true };
-var result = Terser.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 = Terser.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 Terser API does not throw errors.
-To achieve a similar effect one could do the following:
-```javascript
-var result = Terser.minify(code, options);
-if (result.error) throw result.error;
-```
-
-## Minify options
-
-- `ecma` (default `undefined`) - pass `5`, `2015`, `2016`, etc to override `parse`,
- `compress` and `output`'s `ecma` 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).
-
-- `module` (default `false`) — Use when minifying an ES6 module. "use strict"
- is implied and names can be mangled on the top scope. If `compress` or
- `mangle` is enabled then the `toplevel` option will be enabled.
-
-- `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_classnames` (default: `undefined`) - pass `true` to prevent discarding or mangling
- of class names. Pass a regular expression to only keep class names matching that regex.
-
-- `keep_fnames` (default: `false`) - pass `true` to prevent discarding or mangling
- of function names. Pass a regular expression to only keep class names matching that regex.
- Useful for code relying on `Function.prototype.name`. If the top level minify option
- `keep_classnames` is `undefined` it will be overridden with the value of the top level
- minify option `keep_fnames`.
-
-- `safari10` (default: `false`) - pass `true` to work around Safari 10/11 bugs in
- loop scoping and `await`. See `safari10` options in [`mangle`](#mangle-options)
- and [`output`](#output-options) for details.
-
-## Minify options structure
-
-```javascript
-{
- parse: {
- // parse options
- },
- compress: {
- // compress options
- },
- mangle: {
- // mangle options
-
- properties: {
- // mangle property options
- }
- },
- output: {
- // output options
- },
- sourceMap: {
- // source map options
- },
- ecma: 5, // specify one of: 5, 2015, 2016, etc.
- keep_classnames: false,
- keep_fnames: false,
- ie8: false,
- module: false,
- nameCache: null, // or specify a name cache object
- safari10: false,
- toplevel: false,
- warnings: false,
-}
-```
-
-### Source map options
-
-To generate a source map:
-```javascript
-var result = Terser.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 = Terser.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 = Terser.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`.
-
-If you happen to need the source map as a raw object, set `sourceMap.asObject` to `true`.
-
-## Parse options
-
-- `bare_returns` (default `false`) -- support top level `return` statements
-
-- `ecma` (default: `2017`) -- specify one of `5`, `2015`, `2016` or `2017`. Note: this setting
- is not presently enforced except for ES8 optional trailing commas in function
- parameter lists and calls with `ecma` `2017`.
-
-- `html5_comments` (default `true`)
-
-- `shebang` (default `true`) -- support `#!command` as the first line
-
-## Compress options
-
-- `defaults` (default: `true`) -- Pass `false` to disable most default
- enabled `compress` transforms. Useful when you only want to enable a few
- `compress` options while disabling the rest.
-
-- `arrows` (default: `true`) -- Class and object literal methods are converted
- will also be converted to arrow expressions if the resultant code is shorter:
- `m(){return x}` becomes `m:()=>x`. To do this to regular ES5 functions which
- don't use `this` or `arguments`, see `unsafe_arrows`.
-
-- `arguments` (default: `false`) -- 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`
-
-- `booleans_as_integers` (default: `false`) -- Turn booleans into 0 and 1, also
- makes comparisons with booleans use `==` and `!=` instead of `===` and `!==`.
-
-- `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` (only when `unsafe_comps`), attempts to negate binary
- nodes, e.g. `a = !b && !c && !d && !e → a=!(b||c||d||e)` etc.
-
-- `computed_props` (default: `true`) -- Transforms constant computed properties
- into regular ones: `{["computed"]: 1}` is converted to `{computed: 1}`.
-
-- `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
-
-- `ecma` (default: `5`) -- Pass `2015` or greater to enable `compress` options that
- will transform ES5 code into smaller ES6+ equivalent forms.
-
-- `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_classnames` (default: `false`) -- Pass `true` to prevent the compressor from
- discarding class names. Pass a regular expression to only keep class names matching
- that regex. See also: the `keep_classnames` [mangle option](#mangle).
-
-- `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. Pass a regular expression to only keep
- function names matching that regex. 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.
-
-- `module` (default `false`) -- Pass `true` when compressing an ES6 module. Strict
- mode is implied and the `toplevel` option as well.
-
-- `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
- Terser 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, Terser 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).
-
-- `pure_getters` (default: `"strict"`) -- If you pass `true` for
- this, Terser 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` (legacy option, safely ignored for backwards compatibility).
-
-- `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
- function calls 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
- ([details](#the-unsafe-compress-option)).
-
-- `unsafe_arrows` (default: `false`) -- Convert ES5 style anonymous function
- expressions to arrow functions if the function body does not reference `this`.
- Note: it is not always safe to perform this conversion if code relies on the
- the function having a `prototype`, which arrow functions lack.
- This transform requires that the `ecma` compress option is set to `2015` or greater.
-
-- `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.
-
-- `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_symbols` (default: `false`) -- removes keys from native Symbol
- declarations, e.g `Symbol("kDog")` becomes `Symbol()`.
-
-- `unsafe_methods` (default: false) -- Converts `{ m: function(){} }` to
- `{ m(){} }`. `ecma` must be set to `6` or greater to enable this transform.
- If `unsafe_methods` is a RegExp then key/value pairs with keys matching the
- RegExp will be converted to concise methods.
- Note: if enabled there is a risk of getting a "`<method name>` is not a
- constructor" TypeError should any code try to `new` the former function.
-
-- `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_classnames` (default `false`) -- Pass `true` to not mangle class names.
- Pass a regular expression to only keep class names matching that regex.
- See also: the `keep_classnames` [compress option](#compress-options).
-
-- `keep_fnames` (default `false`) -- Pass `true` to not mangle function names.
- Pass a regular expression to only keep class names matching that regex.
- Useful for code relying on `Function.prototype.name`. See also: the `keep_fnames`
- [compress option](#compress-options).
-
-- `module` (default `false`) -- Pass `true` an ES6 modules, where the toplevel
- scope is not the global scope. Implies `toplevel`.
-
-- `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.
-
-- `safari10` (default `false`) -- Pass `true` to work around the Safari 10 loop
- iterator [bug](https://bugs.webkit.org/show_bug.cgi?id=171041)
- "Cannot declare a let variable twice".
- See also: the `safari10` [output option](#output-options).
-
-Examples:
-
-```javascript
-// test.js
-var globalVar;
-function funcName(firstLongName, anotherLongName) {
- var myVariable = firstLongName + anotherLongName;
-}
-```
-```javascript
-var code = fs.readFileSync("test.js", "utf8");
-
-Terser.minify(code).code;
-// 'function funcName(a,n){}var globalVar;'
-
-Terser.minify(code, { mangle: { reserved: ['firstLongName'] } }).code;
-// 'function funcName(firstLongName,a){}var globalVar;'
-
-Terser.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.
- - `true` -- Quoted property names are automatically reserved and any unquoted
- property names will not be mangled.
- - `"strict"` -- Advanced, all unquoted property names are mangled unless
- explicitly reserved.
-
-- `regex` (default: `null`) — Pass a [RegExp literal or pattern string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp) to only mangle property matching the regular expression.
-
-- `reserved` (default: `[]`) — Do not mangle property names listed in the
- `reserved` array.
-
-- `undeclared` (default: `false`) - Mangle those names when they are accessed
- as properties of known top level variables but their declarations are never
- found in input code. May be useful when only minifying parts of a project.
- See [#397](https://github.com/terser/terser/issues/397) for more details.
-
-## 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 `"some"`) -- by default it keeps JSDoc-style comments
- that contain "@license" or "@preserve", pass `true` or `"all"` to preserve all
- comments, `false` to omit comments in the output, a regular expression string
- (e.g. `/^!/`) or a function.
-
-- `ecma` (default `5`) -- set output printing mode. Set `ecma` to `2015` or
- greater to emit shorthand object properties - i.e.: `{a}` instead of `{a: a}`.
- The `ecma` option will only change the output in direct control of the
- beautifier. Non-compatible features in the abstract syntax tree will still
- be output as is. For example: an `ecma` setting of `5` will **not** convert
- ES6+ code to ES5.
-
-- `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_numbers` (default `false`) -- keep number literals as it was in original code
- (disables optimizations like converting `1000000` into `1e6`)
-
-- `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 minified 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.
-
-- `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
-
-- `preserve_annotations` -- (default `false`) -- Preserve [Terser annotations](#annotations) in the output.
-
-- `safari10` (default `false`) -- set this option to `true` to work around
- the [Safari 10/11 await bug](https://bugs.webkit.org/show_bug.cgi?id=176685).
- See also: the `safari10` [mangle option](#mangle-options).
-
-- `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 minified 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`.
-
-- `wrap_iife` (default `false`) -- pass `true` to wrap immediately invoked
- function expressions. See
- [#640](https://github.com/mishoo/UglifyJS2/issues/640) for more details.
-
-- `wrap_func_args` (default `true`) -- pass `false` if you do not want to wrap
- function expressions that are passed as arguments, in parenthesis. See
- [OptimizeJS](https://github.com/nolanlawson/optimize-js) 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. It assumes that standard
-built-in ECMAScript functions and classes have not been altered or replaced.
-You might want to try it on your own code; it should reduce the minified size.
-Some examples of the optimizations made when this option is enabled:
-
-- `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`
-- `"foo bar".substr(4)` → `"bar"`
-
-### Conditional compilation
-
-You can use the `--define` (`-d`) switch in order to declare global
-variables that Terser will assume to be constants (unless defined in
-scope). For example if you pass `--define DEBUG=false` then, coupled with
-dead code removal Terser 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`.
-
-Terser 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:
-
- terser build/defines.js js/foo.js js/bar.js... -c
-
-Terser 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 = Terser.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 Terser
-to parse the value as an expression:
-```javascript
-Terser.minify("alert('hello');", {
- compress: {
- global_defs: {
- "@alert": "console.log"
- }
- }
-}).code;
-// returns: 'console.log("hello");'
-```
-
-Otherwise it would be replaced as string literal:
-```javascript
-Terser.minify("alert('hello');", {
- compress: {
- global_defs: {
- "alert": "console.log"
- }
- }
-}).code;
-// returns: '"console.log"("hello");'
-```
-
-### Using native Terser AST with `minify()`
-```javascript
-// example: parse only, produce native Terser AST
-
-var result = Terser.minify(code, {
- parse: {},
- compress: false,
- mangle: false,
- output: {
- ast: true,
- code: false // optional - faster if false
- }
-});
-
-// result.ast contains native Terser AST
-```
-```javascript
-// example: accept native Terser AST input and then compress and mangle
-// to produce both code and native AST.
-
-var result = Terser.minify(ast, {
- compress: {},
- mangle: {},
- output: {
- ast: true,
- code: true // optional - faster if false
- }
-});
-
-// result.ast contains native Terser AST
-// result.code contains the minified code in string form.
-```
-
-
-### Annotations
-
-Annotations in Terser are a way to tell it to treat a certain function call differently. The following annotations are available:
-
- * `/*@__INLINE__*/` - forces a function to be inlined somewhere.
- * `/*@__NOINLINE__*/` - Makes sure the called function is not inlined into the call site.
- * `/*@__PURE__*/` - Marks a function call as pure. That means, it can safely be dropped.
-
-You can use either a `@` sign at the start, or a `#`.
-
-Here are some examples on how to use them:
-
-```javascript
-/*@__INLINE__*/
-function_always_inlined_here()
-
-/*#__NOINLINE__*/
-function_cant_be_inlined_into_here()
-
-const x = /*#__PURE__*/i_am_dropped_if_x_is_not_used()
-```
-
-
-### Working with Terser AST
-
-Traversal and transformation of the native AST can be performed through
-[`TreeWalker`](https://github.com/fabiosantoscode/terser/blob/master/lib/ast.js) and
-[`TreeTransformer`](https://github.com/fabiosantoscode/terser/blob/master/lib/transform.js)
-respectively.
-
-Largely compatible native AST examples can be found in the original UglifyJS
-documentation. See: [tree walker](http://lisperator.net/uglifyjs/walk) and
-[tree transform](http://lisperator.net/uglifyjs/transform).
-
-### ESTree / SpiderMonkey AST
-
-Terser 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,
-Terser 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 Terser to mangle and
-compress that:
-
- acorn file.js | terser -p spidermonkey -m -c
-
-The `-p spidermonkey` option tells Terser 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, Terser 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 Terser's own parser.
-
-[acorn]: https://github.com/ternjs/acorn
-[sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k
-
-### Terser 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
-Terser builds by 3 to 4 times.
-
-| d3.js | size | gzip size | time (s) |
-| --- | ---: | ---: | ---: |
-| original | 451,131 | 108,733 | - |
-| terser@3.7.5 mangle=false, compress=false | 316,600 | 85,245 | 0.82 |
-| terser@3.7.5 mangle=true, compress=false | 220,216 | 72,730 | 1.45 |
-| terser@3.7.5 mangle=true, compress=true | 212,046 | 70,954 | 5.87 |
-| babili@0.1.4 | 210,713 | 72,140 | 12.64 |
-| babel-minify@0.4.3 | 210,321 | 72,242 | 48.67 |
-| babel-minify@0.5.0-alpha.01eac1c3 | 210,421 | 72,238 | 14.17 |
-
-To enable fast minify mode from the CLI use:
-```
-terser file.js -m
-```
-To enable fast minify mode with the API use:
-```js
-Terser.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 `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()`).
-- `document.all` is not `== null`
-- Assigning properties to a class doesn't have side effects and does not throw.
-
-### Build Tools and Adaptors using Terser
-
-https://www.npmjs.com/browse/depended/terser
-
-### Replacing `uglify-es` with `terser` in a project using `yarn`
-
-A number of JS bundlers and uglify wrappers are still using buggy versions
-of `uglify-es` and have not yet upgraded to `terser`. If you are using `yarn`
-you can add the following alias to your project's `package.json` file:
-
-```js
- "resolutions": {
- "uglify-es": "npm:terser"
- }
-```
-
-to use `terser` instead of `uglify-es` in all deeply nested dependencies
-without changing any code.
-
-Note: for this change to take effect you must run the following commands
-to remove the existing `yarn` lock file and reinstall all packages:
-
-```
-$ rm -rf node_modules yarn.lock
-$ yarn
-```
-
-# Reporting issues
-
-In the terser CLI we use [source-map-support](https://npmjs.com/source-map-support) to produce good error stacks. In your own app, you're expected to enable source-map-support (read their docs) to have nice stack traces that will make good issues.
-
-# README.md Patrons:
-
-*note*: You can support this project on patreon: <a target="_blank" rel="nofollow" href="https://www.patreon.com/fabiosantoscode"><img src="https://c5.patreon.com/external/logo/become_a_patron_button@2x.png" alt="patron" width="100px" height="auto"></a>. Check out [PATRONS.md](https://github.com/terser/terser/blob/master/PATRONS.md) for our first-tier patrons.
-
-These are the second-tier patrons. Great thanks for your support!
-
- * CKEditor ![](https://c10.patreonusercontent.com/3/eyJoIjoxMDAsInciOjEwMH0%3D/patreon-media/p/user/15452278/f8548dcf48d740619071e8d614459280/1?token-time=2145916800&token-hash=SIQ54PhIPHv3M7CVz9LxS8_8v4sOw4H304HaXsXj8MM%3D)
- * 38elements ![](https://c10.patreonusercontent.com/3/eyJ3IjoyMDB9/patreon-media/p/user/12501844/88e7fc5dd62d45c6a5626533bbd48cfb/1?token-time=2145916800&token-hash=c3AsQ5T0IQWic0zKxFHu-bGGQJkXQFvafvJ4bPerFR4%3D)
-
-## Contributors
-
-### Code Contributors
-
-This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
-<a href="https://github.com/terser/terser/graphs/contributors"><img src="https://opencollective.com/terser/contributors.svg?width=890&button=false" /></a>
-
-### Financial Contributors
-
-Become a financial contributor and help us sustain our community. [[Contribute](https://opencollective.com/terser/contribute)]
-
-#### Individuals
-
-<a href="https://opencollective.com/terser"><img src="https://opencollective.com/terser/individuals.svg?width=890"></a>
-
-#### Organizations
-
-Support this project with your organization. Your logo will show up here with a link to your website. [[Contribute](https://opencollective.com/terser/contribute)]
-
-<a href="https://opencollective.com/terser/organization/0/website"><img src="https://opencollective.com/terser/organization/0/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/1/website"><img src="https://opencollective.com/terser/organization/1/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/2/website"><img src="https://opencollective.com/terser/organization/2/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/3/website"><img src="https://opencollective.com/terser/organization/3/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/4/website"><img src="https://opencollective.com/terser/organization/4/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/5/website"><img src="https://opencollective.com/terser/organization/5/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/6/website"><img src="https://opencollective.com/terser/organization/6/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/7/website"><img src="https://opencollective.com/terser/organization/7/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/8/website"><img src="https://opencollective.com/terser/organization/8/avatar.svg"></a>
-<a href="https://opencollective.com/terser/organization/9/website"><img src="https://opencollective.com/terser/organization/9/avatar.svg"></a>