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					1375 lines
				
				57 KiB
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											3 years ago
										 | <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 mangler/compressor toolkit for ES6+. | ||
|  | 
 | ||
|  | *note*: <s>You can support this project on patreon: [link]</s> **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 | ||
|  | [travis-image]: https://app.travis-ci.com/terser/terser.svg?branch=master | ||
|  | [travis-url]: https://app.travis-ci.com/github/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|  | `uglify-es` is [no longer maintained](https://github.com/mishoo/UglifyJS2/issues/3156#issuecomment-392943058) and `uglify-js` does not support ES6+.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
 | ||
|  | 
 | ||
|  | <!-- CLI_USAGE:START --> | ||
|  | 
 | ||
|  |     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 <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. | ||
|  |     -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 <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 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 <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 `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 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 `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 <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. | ||
|  | 
 | ||
|  | <!-- CLI_USAGE:END --> | ||
|  | 
 | ||
|  | # API Reference
 | ||
|  | 
 | ||
|  | <!-- API_REFERENCE:START --> | ||
|  | 
 | ||
|  | 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: | ||
|  | ```html | ||
|  | <script src="https://cdn.jsdelivr.net/npm/source-map@0.7.3/dist/source-map.js"></script> | ||
|  | <script src="https://cdn.jsdelivr.net/npm/terser/dist/bundle.min.js"></script> | ||
|  | ``` | ||
|  | 
 | ||
|  | There is a single 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 | ||
|  | ``` | ||
|  | 
 | ||
|  | 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][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 = 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. | ||
|  | 
 | ||
|  | - `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-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. | ||
|  | 
 | ||
|  | - `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_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. 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"`) | ||
|  | 
 | ||
|  | ## 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`. | ||
|  | 
 | ||
|  | - `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_identifer` (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 `</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) | ||
|  | 
 | ||
|  | - `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 `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 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. | ||
|  | 
 | ||
|  | 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() | ||
|  | ``` | ||
|  | 
 | ||
|  | ### 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. | ||
|  | 
 | ||
|  | `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. | ||
|  | 
 | ||
|  | [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 | ||
|  | 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`. | ||
|  | 
 | ||
|  | ### 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 | ||
|  | ``` | ||
|  | 
 | ||
|  | <!-- API_REFERENCE:END --> | ||
|  | 
 | ||
|  | # 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 help you write good issues. | ||
|  | 
 | ||
|  | ## 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. If you're using a bundler or a project that includes a bundler and are not sure what went wrong with your code, pass that variable like so: | ||
|  | 
 | ||
|  | ``` | ||
|  | $ TERSER_DEBUG_DIR=/path/to/logs command-that-uses-terser | ||
|  | $ ls /path/to/logs | ||
|  | 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
 | ||
|  | ``` | ||
|  | 
 | ||
|  | # README.md Patrons:
 | ||
|  | 
 | ||
|  | *note*: <s>You can support this project on patreon: [link]</s> **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)]. | ||
|  | <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> |