Index: frontend/node_modules/terser/README.md
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+
+
+ [![NPM Version][npm-image]][npm-url]
+ [![NPM Downloads][downloads-image]][downloads-url]
+ [![CI pipeline][ci-image]][ci-url]
+ [![Opencollective financial contributors][opencollective-contributors]][opencollective-url]
+
+A JavaScript mangler/compressor toolkit for ES6+.
+
+*note*: You can support this project on patreon: [link] **The Terser Patreon is shutting down in favor of opencollective**. 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
+[ci-image]: https://github.com/terser/terser/actions/workflows/ci.yml/badge.svg
+[ci-url]: https://github.com/terser/terser/actions/workflows/ci.yml
+[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+`uglify-es` is [no longer maintained](https://github.com/mishoo/UglifyJS2/issues/3156#issuecomment-392943058) and `uglify-js` does not support ES6+.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.
+
+Command line arguments that take options (like --parse, --compress, --mangle and
+--format) can take in a comma-separated list of default option overrides. For
+instance:
+
+ terser input.js --compress ecma=2015,computed_props=false
+
+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 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.
+ `only_annotated` Only mangle properties defined with /*@__MANGLE_PROP__*/.
+ `reserved` List of names that should not be mangled.
+ -f, --format [options] Specify format 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 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 e.g. "@license",
+ or start with "!". 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 Read `minify()` options from JSON file.
+ -d, --define [=value] Global definitions.
+ --ecma 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 `format` 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, as well as strict mode,
+ will be enabled.
+ --name-cache File to hold mangled name mappings.
+ --safari10 Support non-standard Safari 10/11.
+ Equivalent to setting `safari10: true` in `minify()`
+ for `mangle` and `format` 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.
+ --wrap Embed everything in a big function, making the
+ “exports” and “global” variables available. You
+ need to pass an argument to this option to
+ specify the name that your module will take
+ when included in, say, a browser.
+```
+
+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=''"` to specify the name of the source map.
+
+- `--source-map "root=''"` to pass the URL where the original files can be found.
+
+- `--source-map "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
+const { minify } = require("terser");
+```
+
+Or,
+
+```javascript
+import { minify } from "terser";
+```
+
+Browser loading is also supported. It exposes a global variable `Terser` containing a `.minify` property:
+```html
+
+
+```
+
+There is an async high level function, **`async minify(code, options)`**,
+which will perform all minification [phases](#minify-options) in a configurable
+manner. By default `minify()` will enable [`compress`](#compress-options)
+and [`mangle`](#mangle-options). Example:
+```javascript
+var code = "function add(first, second) { return first + second; }";
+var result = await minify(code, { sourceMap: true });
+console.log(result.code); // minified output: function add(n,d){return n+d}
+console.log(result.map); // source map
+```
+
+There is also a `minify_sync()` alternative version of it, which returns instantly.
+
+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 = await 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 = await minify(code, options);
+console.log(result.code);
+// console.log(3+7);
+```
+
+The `nameCache` option:
+```javascript
+var options = {
+ mangle: {
+ toplevel: true,
+ },
+ nameCache: {}
+};
+var result1 = await minify({
+ "file1.js": "function add(first, second) { return first + second; }"
+}, options);
+var result2 = await 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", await minify({
+ "file1.js": fs.readFileSync("file1.js", "utf8"),
+ "file2.js": fs.readFileSync("file2.js", "utf8")
+}, options).code, "utf8");
+fs.writeFileSync("part2.js", await 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
+ },
+ format: {
+ preamble: "/* minified */"
+ }
+};
+var result = await minify(code, options);
+console.log(result.code);
+// /* minified */
+// alert(10);"
+```
+
+An error example:
+```javascript
+try {
+ const result = await minify({"foo.js" : "if (0) else console.log(1);"});
+ // Do something with result
+} catch (error) {
+ const { message, filename, line, col, pos } = error;
+ // Do something with error
+}
+```
+
+## Minify options
+
+- `ecma` (default `undefined`) - pass `5`, `2015`, `2016`, etc to override
+ `compress` and `format`'s `ecma` options.
+
+- `enclose` (default `false`) - pass `true`, or a string in the format
+ of `"args[:values]"`, where `args` and `values` are comma-separated
+ argument names and values, respectively, to embed the output in a big
+ function with the configurable arguments and values.
+
+- `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.
+
+- `format` or `output` (default `null`) — pass an object if you wish to specify
+ additional [format options](#format-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 function 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 [`format`](#format-options) for details.
+
+## Minify options structure
+
+```javascript
+{
+ parse: {
+ // parse options
+ },
+ compress: {
+ // compress options
+ },
+ mangle: {
+ // mangle options
+
+ properties: {
+ // mangle property options
+ }
+ },
+ format: {
+ // format options (can also use `output` for backwards compatibility)
+ },
+ sourceMap: {
+ // source map options
+ },
+ ecma: 5, // specify one of: 5, 2015, 2016, etc.
+ enclose: false, // or specify true, or "args:values"
+ keep_classnames: false,
+ keep_fnames: false,
+ ie8: false,
+ module: false,
+ nameCache: null, // or specify a name cache object
+ safari10: false,
+ toplevel: false
+}
+```
+
+### Source map options
+
+To generate a source map:
+```javascript
+var result = await 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](https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k))
+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 = await 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 = await 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
+
+- `html5_comments` (default `true`)
+
+- `shebang` (default `true`) -- support `#!command` as the first line
+
+- `spidermonkey` (default `false`) -- accept a Spidermonkey (Mozilla) AST
+
+## 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. Note: `comparisons`
+ works best with `lhs_constants` enabled.
+
+- `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 only want to discard a portion of console,
+ you can pass an array like this `['log', 'info']`, which will only discard `console.log`、 `console.info`.
+
+- `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.
+
+- `builtins_ecma` (default: `5`) -- An ES version number (like `ecma`). Tells Terser which well-known functions, constants, methods and classes are available in the global object. Does nothing by itself, but is used by `builtins_pure` and `unsafe`.
+
+- `builtins_pure` (default: `false`) -- Pass `true` to assume that functions matched by the `builtins_ecma` option (such as `Math.sin` or `unescape`) are pure and calls to them can be removed.
+
+- `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`, `let` and `const` 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-options).
+
+- `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-options).
+
+- `keep_infinity` (default: `false`) -- Pass `true` to prevent `Infinity` from
+ being compressed into `1/0`, which may cause performance issues on Chrome.
+
+- `lhs_constants` (default: `true`) -- Moves constant values to the left-hand side
+ of binary nodes. `foo == 42 → 42 == foo`
+
+- `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`.
+
+- `pure_new` (default: `false`) -- Set to `true` to assume `new X()` never has
+ side effects.
+
+- `reduce_vars` (default: `true`) -- Improve optimization on variables assigned with and
+ used as constant values.
+
+- `reduce_funcs` (default: `true`) -- Inline single-use functions when
+ possible. Depends on `reduce_vars` being enabled. Disabling this option
+ sometimes improves performance of the output code.
+
+- `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`) -- Remove expressions which have no side effects
+ and whose results aren't used.
+
+- `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. Or if one of two operands is `NaN`, the result is always
+ `false`. 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 "`` 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"`)
+
+## 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 function 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` and assumes input code is strict mode JS.
+
+- `nth_identifier` (default: an internal mangler that weights based on character
+ frequency analysis) -- Pass an object with a `get(n)` function that converts an
+ ordinal into the nth most favored (usually shortest) identifier.
+ Optionally also provide `reset()`, `sort()`, and `consider(chars, delta)` to
+ use character frequency analysis of the source code.
+
+- `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` [format option](#format-options).
+
+Examples:
+
+```javascript
+// test.js
+var globalVar;
+function funcName(firstLongName, anotherLongName) {
+ var myVariable = firstLongName + anotherLongName;
+}
+```
+```javascript
+var code = fs.readFileSync("test.js", "utf8");
+
+await minify(code).code;
+// 'function funcName(a,n){}var globalVar;'
+
+await minify(code, { mangle: { reserved: ['firstLongName'] } }).code;
+// 'function funcName(firstLongName,a){}var globalVar;'
+
+await 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`) — How quoting properties (`{"prop": ...}` and `obj["prop"]`) controls what gets mangled.
+ - `"strict"` (recommended) -- `obj.prop` is mangled.
+ - `false` -- `obj["prop"]` is mangled.
+ - `true` -- `obj.prop` is mangled unless there is `obj["prop"]` elsewhere in the code.
+
+- `nth_identifier` (default: an internal mangler that weights based on character
+ frequency analysis) -- Pass an object with a `get(n)` function that converts an
+ ordinal into the nth most favored (usually shortest) identifier.
+ Optionally also provide `reset()`, `sort()`, and `consider(chars, delta)` to
+ use character frequency analysis of the source code.
+
+- `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.
+
+
+## Format options
+
+These options control the format of Terser's output code. Previously known
+as "output options".
+
+- `ascii_only` (default `false`) -- escape Unicode characters in strings and
+ regexps (affects directives with non-ascii characters becoming invalid)
+
+- `beautify` (default `false`) -- (DEPRECATED) whether to beautify the output.
+ When using the legacy `-b` CLI flag, this is set to true by default.
+
+- `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", "@copyright", "@preserve" or start with `!`, 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 desired EcmaScript standard version for output.
+ 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 your input will
+ still be output as is. For example: an `ecma` setting of `5` will **not**
+ convert modern 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 `` 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)
+
+- `spidermonkey` (default `false`) -- produce a Spidermonkey (Mozilla) AST
+
+- `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 `false`) -- pass `true` in order 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 comments starting with "!" and JSDoc-style comments that
+contain "@preserve", "@copyright", "@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 ]`
+- `Array.from([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`.
+
+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 = await 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
+await minify("alert('hello');", {
+ compress: {
+ global_defs: {
+ "@alert": "console.log"
+ }
+ }
+}).code;
+// returns: 'console.log("hello");'
+```
+
+Otherwise it would be replaced as string literal:
+```javascript
+await minify("alert('hello');", {
+ compress: {
+ global_defs: {
+ "alert": "console.log"
+ }
+ }
+}).code;
+// returns: '"console.log"("hello");'
+```
+
+### 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.
+ * `/*@__KEY__*/` - Marks a string literal as a property to also mangle it when mangling properties.
+ * `/*@__MANGLE_PROP__*/` - Opts-in an object property (or class field) for mangling, when the property mangler is enabled.
+
+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()
+
+function lookup(object, key) { return object[key]; }
+lookup({ i_will_be_mangled_too: "bar" }, /*@__KEY__*/ "i_will_be_mangled_too");
+```
+
+### 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](https://github.com/acornjs/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.
+
+`spidermonkey` is also available in `minify` as `parse` and `format` options to
+accept and/or produce a spidermonkey 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.
+
+### 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
+await 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`.
+
+When debugging, make sure you enable the **"map scopes"** feature to map mangled variable names back to their original names.
+Without this, all variable values will be `undefined`. See https://github.com/terser/terser/issues/1367 for more details.
+
+
+
+
+### 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
+
+
+
+## A minimal, reproducible example
+
+You're expected to provide a [minimal reproducible example] of input code that will demonstrate your issue.
+
+To get to this example, you can remove bits of your code and stop if your issue ceases to reproduce.
+
+## Obtaining the source code given to Terser
+
+Because users often don't control the call to `await minify()` or its arguments, Terser provides a `TERSER_DEBUG_DIR` environment variable to make terser output some debug logs.
+
+These logs will contain the input code and options of each `minify()` call.
+
+```bash
+TERSER_DEBUG_DIR=/tmp/terser-log-dir command-that-uses-terser
+ls /tmp/terser-log-dir
+terser-debug-123456.log
+```
+
+If you're not sure how to set an environment variable on your shell (the above example works in bash), you can try using cross-env:
+
+```
+> npx cross-env TERSER_DEBUG_DIR=/path/to/logs command-that-uses-terser
+```
+
+## Stack traces
+
+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 help you write good issues.
+
+
+
+# README.md Patrons:
+
+*note*: You can support this project on patreon: [link] **The Terser Patreon is shutting down in favor of opencollective**. 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 
+ * 38elements 
+
+## Contributors
+
+### Code Contributors
+
+This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
+
+
+### Financial Contributors
+
+Become a financial contributor and help us sustain our community. [[Contribute](https://opencollective.com/terser/contribute)]
+
+#### Individuals
+
+
+
+#### 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)]
+
+
+
+
+
+
+
+
+
+
+