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diff --git a/node_modules/uglify-js/README.md b/node_modules/uglify-js/README.md index 8c1d67642..8db77e57e 100644 --- a/node_modules/uglify-js/README.md +++ b/node_modules/uglify-js/README.md @@ -1,20 +1,14 @@ -UglifyJS 2 +UglifyJS 3 ========== -[](https://travis-ci.org/mishoo/UglifyJS2) -UglifyJS is a JavaScript parser, minifier, compressor or beautifier toolkit. - -This page documents the command line utility. For -[API and internals documentation see my website](http://lisperator.net/uglifyjs/). -There's also an -[in-browser online demo](http://lisperator.net/uglifyjs/#demo) (for Firefox, -Chrome and probably Safari). +UglifyJS is a JavaScript parser, minifier, compressor and beautifier toolkit. #### Note: +- **`uglify-js@3` has a simplified [API](#api-reference) and [CLI](#command-line-usage) that is not backwards compatible with [`uglify-js@2`](https://github.com/mishoo/UglifyJS2/tree/v2.x)**. +- **Documentation for UglifyJS `2.x` releases can be found [here](https://github.com/mishoo/UglifyJS2/tree/v2.x)**. - `uglify-js` only supports ECMAScript 5 (ES5). -- Support for `const` is [present but incomplete](#support-for-const), and may not be - transformed properly. -- Those wishing to minify ES2015+ (ES6+) should use the `npm` package [**uglify-es**](https://github.com/mishoo/UglifyJS2/tree/harmony). +- Those wishing to minify +ES2015+ (ES6+) should use the `npm` package [**uglify-es**](https://github.com/mishoo/UglifyJS2/tree/harmony). Install ------- @@ -30,70 +24,74 @@ From NPM for programmatic use: npm install uglify-js -Usage ------ +# Command line usage uglifyjs [input files] [options] -UglifyJS2 can take multiple input files. It's recommended that you pass the +UglifyJS can take multiple input files. It's recommended that you pass the input files first, then pass the options. UglifyJS will parse input files in sequence and apply any compression options. The files are parsed in the same global scope, that is, a reference from a file to some variable/function declared in another file will be matched properly. -If you want to read from STDIN instead, pass a single dash instead of input -files. +If no input file is specified, UglifyJS will read from STDIN. If you wish to pass your options before the input files, separate the two with a double dash to prevent input files being used as option arguments: uglifyjs --compress --mangle -- input.js -The available options are: - -``` - --source-map Specify an output file where to generate source - map. - --source-map-root The path to the original source to be included - in the source map. - --source-map-url The path to the source map to be added in //# - sourceMappingURL. Defaults to the value passed - with --source-map. - --source-map-include-sources Pass this flag if you want to include the - content of source files in the source map as - sourcesContent property. - --source-map-inline Write base64-encoded source map to the end of js output. - --in-source-map 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 - inline with the sources. - --screw-ie8 Use this flag if you don't wish to support - Internet Explorer 6/7/8. - By default UglifyJS will not try to be IE-proof. - --support-ie8 Use this flag to support Internet Explorer 6/7/8. - Equivalent to setting `screw_ie8: false` in `minify()` - for `compress`, `mangle` and `output` options. - --expr Parse a single expression, rather than a - program (for parsing JSON) - -p, --prefix Skip prefix for original filenames that appear - in source maps. For example -p 3 will drop 3 - directories from file names and ensure they are - relative paths. You can also specify -p - relative, which will make UglifyJS figure out - itself the relative paths between original - sources, the source map and the output file. - -o, --output Output file (default STDOUT). - -b, --beautify Beautify output/specify output options. - -m, --mangle Mangle names/pass mangler options. - -r, --reserved Reserved names to exclude from mangling. - -c, --compress Enable compressor/pass compressor options, e.g. - `-c 'if_return=false,pure_funcs=["Math.pow","console.log"]'` - Use `-c` with no argument to enable default compression - options. - -d, --define Global definitions - -e, --enclose Embed everything in a big function, with a - configurable parameter/argument list. - --comments Preserve copyright comments in the output. By +### Command line options + +``` + -h, --help Print usage information. + `--help options` for details on available options. + -V, --version Print version number. + -p, --parse <options> Specify parser options: + `acorn` Use Acorn for parsing. + `bare_returns` Allow return outside of functions. + Useful when minifying CommonJS + modules and Userscripts that may + be anonymous function wrapped (IIFE) + by the .user.js engine `caller`. + `expression` Parse a single expression, rather than + a program (for parsing JSON). + `spidermonkey` Assume input files are SpiderMonkey + AST format (as JSON). + -c, --compress [options] Enable compressor/specify compressor options: + `pure_funcs` List of functions that can be safely + removed when their return values are + not used. + -m, --mangle [options] Mangle names/specify mangler options: + `reserved` List of names that should not be mangled. + --mangle-props [options] Mangle properties/specify mangler options: + `builtins` Mangle property names that overlaps + with standard JavaScript globals. + `debug` Add debug prefix and suffix. + `domprops` Mangle property names that overlaps + with DOM properties. + `keep_quoted` Only mangle unquoted properies. + `regex` Only mangle matched property names. + `reserved` List of names that should not be mangled. + -b, --beautify [options] Beautify output/specify output options: + `beautify` Enabled with `--beautify` by default. + `preamble` Preamble to prepend to the output. You + can use this to insert a comment, for + example for licensing information. + This will not be parsed, but the source + map will adjust for its presence. + `quote_style` Quote style: + 0 - auto + 1 - single + 2 - double + 3 - original + `wrap_iife` Wrap IIFEs in parenthesis. Note: you may + want to disable `negate_iife` under + compressor options. + -o, --output <file> Output file path (default STDOUT). Specify `ast` or + `spidermonkey` to write UglifyJS or SpiderMonkey AST + as JSON to STDOUT respectively. + --comments [filter] Preserve copyright comments in the output. By default this works like Google Closure, keeping JSDoc-style comments that contain "@license" or "@preserve". You can optionally pass one of the @@ -105,80 +103,66 @@ The available options are: kept when compression is on, because of dead code removal or cascading statements into sequences. - --preamble Preamble to prepend to the output. You can use - this to insert a comment, for example for - licensing information. This will not be - parsed, but the source map will adjust for its - presence. - --stats Display operations run time on STDERR. - --acorn Use Acorn for parsing. - --spidermonkey Assume input files are SpiderMonkey AST format - (as JSON). - --self Build itself (UglifyJS2) as a library (implies - --wrap=UglifyJS --export-all) - --wrap Embed everything in a big function, making the + --config-file <file> Read `minify()` options from JSON file. + -d, --define <expr>[=value] Global definitions. + --ie8 Support non-standard Internet Explorer 8. + Equivalent to setting `ie8: true` in `minify()` + for `compress`, `mangle` and `output` options. + By default UglifyJS will not try to be IE-proof. + --keep-fnames Do not mangle/drop function names. Useful for + code relying on Function.prototype.name. + --name-cache <file> File to hold mangled name mappings. + --self Build UglifyJS as a library (implies --wrap UglifyJS) + --source-map [options] Enable source map/specify source map options: + `base` Path to compute relative paths from input files. + `content` Input source map, useful if you're compressing + JS that was generated from some other original + code. Specify "inline" if the source map is + included within the sources. + `filename` Name and/or location of the output source. + `includeSources` Pass this flag if you want to include + the content of source files in the + source map as sourcesContent property. + `root` Path to the original source to be included in + the source map. + `url` If specified, path to the source map to append in + `//# sourceMappingURL`. + --timings Display operations run time on STDERR. + --toplevel Compress and/or mangle variables in top level scope. + --verbose Print diagnostic messages. + --warn Print warning messages. + --wrap <name> Embed everything in a big function, making the “exports” and “global” variables available. You need to pass an argument to this option to specify the name that your module will take when included in, say, a browser. - --export-all Only used when --wrap, this tells UglifyJS to - add code to automatically export all globals. - --lint Display some scope warnings - -v, --verbose Verbose - -V, --version Print version number and exit. - --noerr Don't throw an error for unknown options in -c, - -b or -m. - --bare-returns Allow return outside of functions. Useful when - minifying CommonJS modules and Userscripts that - may be anonymous function wrapped (IIFE) by the - .user.js engine `caller`. - --keep-fnames Do not mangle/drop function names. Useful for - code relying on Function.prototype.name. - --reserved-file File containing reserved names - --reserve-domprops Make (most?) DOM properties reserved for - --mangle-props - --mangle-props Mangle property names (default `0`). Set to - `true` or `1` to mangle all property names. Set - to `unquoted` or `2` to only mangle unquoted - property names. Mode `2` also enables the - `keep_quoted_props` beautifier option to - preserve the quotes around property names and - disables the `properties` compressor option to - prevent rewriting quoted properties with dot - notation. You can override these by setting - them explicitly on the command line. - --mangle-regex Only mangle property names matching the regex - --name-cache File to hold mangled names mappings - --pure-funcs Functions that can be safely removed if their - return value is not used, e.g. - `--pure-funcs Math.floor console.info` - (requires `--compress`) ``` Specify `--output` (`-o`) to declare the output file. Otherwise the output goes to STDOUT. -## Source map options +## CLI source map options -UglifyJS2 can generate a source map file, which is highly useful for +UglifyJS can generate a source map file, which is highly useful for debugging your compressed JavaScript. To get a source map, pass -`--source-map output.js.map` (full path to the file where you want the -source map dumped). +`--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. -Additionally you might need `--source-map-root` to pass the URL where the -original files can be found. In case you are passing full paths to input -files to UglifyJS, you can use `--prefix` (`-p`) to specify the number of -directories to drop from the path prefix when declaring files in the source -map. +- `--source-map root=<URL>` to pass the URL where the original files can be found. + Otherwise UglifyJS assumes HTTP `X-SourceMap` is being used and will omit the + `//# sourceMappingURL=` directive. + +- `--source-map url=<URL>` to specify the URL where the source map can be found. For example: - uglifyjs /home/doe/work/foo/src/js/file1.js \ - /home/doe/work/foo/src/js/file2.js \ - -o foo.min.js \ - --source-map foo.min.js.map \ - --source-map-root http://foo.com/src \ - -p 5 -c -m + uglifyjs js/file1.js js/file2.js \ + -o foo.min.js -c -m \ + --source-map root="http://foo.com/src",url=foo.min.js.map The above will compress and mangle `file1.js` and `file2.js`, will drop the output in `foo.min.js` and the source map in `foo.min.js.map`. The source @@ -197,90 +181,114 @@ CoffeeScript → compiled JS, UglifyJS can generate a map from CoffeeScript → compressed JS by mapping every token in the compiled JS to its original location. -To use this feature you need to pass `--in-source-map -/path/to/input/source.map` or `--in-source-map inline` if the source map is -included inline with the sources. Normally the input source map should also -point to the file containing the generated JS, so if that's correct you can -omit input files from the command line. +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 -## Mangler options +You need to pass `--compress` (`-c`) to enable the compressor. Optionally +you can pass a comma-separated list of [compress options](#compress-options). + +Options are in the form `foo=bar`, or just `foo` (the latter implies +a boolean option that you want to set `true`; it's effectively a +shortcut for `foo=true`). + +Example: + + uglifyjs file.js -c toplevel,sequences=false + +## CLI mangle options To enable the mangler you need to pass `--mangle` (`-m`). The following (comma-separated) options are supported: -- `toplevel` — mangle names declared in the toplevel scope (disabled by +- `toplevel` — mangle names declared in the top level scope (disabled by default). - `eval` — mangle names visible in scopes where `eval` or `with` are used (disabled by default). When mangling is enabled but you want to prevent certain names from being -mangled, you can declare those names with `--reserved` (`-r`) — pass a +mangled, you can declare those names with `--mangle reserved` — pass a comma-separated list of names. For example: - uglifyjs ... -m -r '$,require,exports' + uglifyjs ... -m reserved=[$,require,exports] to prevent the `require`, `exports` and `$` names from being changed. -### Mangling property names (`--mangle-props`) +### CLI mangling property names (`--mangle-props`) -**Note:** this will probably break your code. Mangling property names is a -separate step, different from variable name mangling. Pass -`--mangle-props`. It will mangle all properties that are seen in some -object literal, or that are assigned to. For example: +**Note:** THIS WILL PROBABLY BREAK YOUR CODE. Mangling property names +is a separate step, different from variable name mangling. Pass +`--mangle-props` to enable it. It will mangle all properties in the +input code with the exception of built in DOM properties and properties +in core javascript classes. For example: -```js +```javascript +// example.js var x = { - foo: 1 + baz_: 0, + foo_: 1, + calc: function() { + return this.foo_ + this.baz_; + } }; - -x.bar = 2; -x["baz"] = 3; -x[condition ? "moo" : "boo"] = 4; -console.log(x.something()); +x.bar_ = 2; +x["baz_"] = 3; +console.log(x.calc()); +``` +Mangle all properties (except for javascript `builtins`): +```bash +$ uglifyjs example.js -c -m --mangle-props +``` +```javascript +var x={o:0,_:1,l:function(){return this._+this.o}};x.t=2,x.o=3,console.log(x.l()); +``` +Mangle all properties except for `reserved` properties: +```bash +$ uglifyjs example.js -c -m --mangle-props reserved=[foo_,bar_] +``` +```javascript +var x={o:0,foo_:1,_:function(){return this.foo_+this.o}};x.bar_=2,x.o=3,console.log(x._()); +``` +Mangle all properties matching a `regex`: +```bash +$ uglifyjs example.js -c -m --mangle-props regex=/_$/ +``` +```javascript +var x={o:0,_:1,calc:function(){return this._+this.o}};x.l=2,x.o=3,console.log(x.calc()); ``` -In the above code, `foo`, `bar`, `baz`, `moo` and `boo` will be replaced -with single characters, while `something()` will be left as is. - -In order for this to be of any use, we should avoid mangling standard JS -names. For instance, if your code would contain `x.length = 10`, then -`length` becomes a candidate for mangling and it will be mangled throughout -the code, regardless if it's being used as part of your own objects or -accessing an array's length. To avoid that, you can use `--reserved-file` -to pass a filename that should contain the names to be excluded from -mangling. This file can be used both for excluding variable names and -property names. It could look like this, for example: - -```js -{ - "vars": [ "define", "require", ... ], - "props": [ "length", "prototype", ... ] -} +Combining mangle properties options: +```bash +$ uglifyjs example.js -c -m --mangle-props regex=/_$/,reserved=[bar_] +``` +```javascript +var x={o:0,_:1,calc:function(){return this._+this.o}};x.bar_=2,x.o=3,console.log(x.calc()); ``` -`--reserved-file` can be an array of file names (either a single -comma-separated argument, or you can pass multiple `--reserved-file` -arguments) — in this case it will exclude names from all those files. +In order for this to be of any use, we avoid mangling standard JS names by +default (`--mangle-props builtins` to override). A default exclusion file is provided in `tools/domprops.json` which should cover most standard JS and DOM properties defined in various browsers. Pass -`--reserve-domprops` to read that in. +`--mangle-props domprops` to disable this feature. -You can also use a regular expression to define which property names should be -mangled. For example, `--mangle-regex="/^_/"` will only mangle property names -that start with an underscore. +A regular expression can be used to define which property names should be +mangled. For example, `--mangle-props regex=/^_/` will only mangle property +names that start with an underscore. When you compress multiple files using this option, in order for them to work together in the end we need to ensure somehow that one property gets -mangled to the same name in all of them. For this, pass `--name-cache -filename.json` and UglifyJS will maintain these mappings in a file which can -then be reused. It should be initially empty. Example: - -``` -rm -f /tmp/cache.json # start fresh -uglifyjs file1.js file2.js --mangle-props --name-cache /tmp/cache.json -o part1.js -uglifyjs file3.js file4.js --mangle-props --name-cache /tmp/cache.json -o part2.js +mangled to the same name in all of them. For this, pass `--name-cache filename.json` +and UglifyJS will maintain these mappings in a file which can then be reused. +It should be initially empty. Example: + +```bash +$ rm -f /tmp/cache.json # start fresh +$ uglifyjs file1.js file2.js --mangle-props --name-cache /tmp/cache.json -o part1.js +$ uglifyjs file3.js file4.js --mangle-props --name-cache /tmp/cache.json -o part2.js ``` Now, `part1.js` and `part2.js` will be consistent with each other in terms @@ -289,38 +297,303 @@ of mangled property names. Using the name cache is not necessary if you compress all your files in a single call to UglifyJS. -#### Mangling unquoted names (`--mangle-props=unquoted` or `--mangle-props=2`) +### 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); ``` -$ echo 'var o={"foo":1, bar:3}; o.foo += o.bar; console.log(o.foo);' | uglifyjs --mangle-props=2 -mc -var o={"foo":1,a:3};o.foo+=o.a,console.log(o.foo); +```bash +$ uglifyjs stuff.js --mangle-props keep_quoted -c -m +``` +```javascript +var o={foo:1,o:3};o.foo+=o.o,console.log(o.foo); ``` -#### Debugging property name mangling +### Debugging property name mangling -You can also pass `--mangle-props-debug` in order to mangle property names +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. -You can also pass a custom suffix using `--mangle-props-debug=XYZ`. This would then +```bash +$ uglifyjs stuff.js --mangle-props debug -c -m +``` +```javascript +var o={_$foo$_:1,_$bar$_:3};o._$foo$_+=o._$bar$_,console.log(o._$foo$_); +``` + +You can also pass a custom suffix using `--mangle-props debug=XYZ`. This would then mangle `o.foo` to `o._$foo$XYZ_`. You can change this each time you compile a script to identify how a property got mangled. One technique is to pass a random number on every compile to simulate mangling changing with different inputs (e.g. as you update the input script with new properties), and to help identify mistakes like writing mangled keys to storage. -## Compressor options -You need to pass `--compress` (`-c`) to enable the compressor. Optionally -you can pass a comma-separated list of options. Options are in the form -`foo=bar`, or just `foo` (the latter implies a boolean option that you want -to set `true`; it's effectively a shortcut for `foo=true`). +# API Reference + +Assuming installation via NPM, you can load UglifyJS in your application +like this: +```javascript +var UglifyJS = require("uglify-js"); +``` + +There is a single high level function, **`minify(code, options)`**, +which will perform all minification [phases](#minify-options) in a configurable +manner. By default `minify()` will enable the options [`compress`](#compress-options) +and [`mangle`](#mangle-options). Example: +```javascript +var code = "function add(first, second) { return first + second; }"; +var result = UglifyJS.minify(code); +console.log(result.error); // runtime error, or `undefined` if no error +console.log(result.code); // minified output: function add(n,d){return n+d} +``` + +You can `minify` more than one JavaScript file at a time by using an object +for the first argument where the keys are file names and the values are source +code: +```javascript +var code = { + "file1.js": "function add(first, second) { return first + second; }", + "file2.js": "console.log(add(1 + 2, 3 + 4));" +}; +var result = UglifyJS.minify(code); +console.log(result.code); +// function add(d,n){return d+n}console.log(add(3,7)); +``` + +The `toplevel` option: +```javascript +var code = { + "file1.js": "function add(first, second) { return first + second; }", + "file2.js": "console.log(add(1 + 2, 3 + 4));" +}; +var options = { toplevel: true }; +var result = UglifyJS.minify(code, options); +console.log(result.code); +// console.log(3+7); +``` + +The `nameCache` option: +```javascript +var options = { + mangle: { + toplevel: true, + }, + nameCache: {} +}; +var result1 = UglifyJS.minify({ + "file1.js": "function add(first, second) { return first + second; }" +}, options); +var result2 = UglifyJS.minify({ + "file2.js": "console.log(add(1 + 2, 3 + 4));" +}, options); +console.log(result1.code); +// function n(n,r){return n+r} +console.log(result2.code); +// console.log(n(3,7)); +``` + +You may persist the name cache to the file system in the following way: +```javascript +var cacheFileName = "/tmp/cache.json"; +var options = { + mangle: { + properties: true, + }, + nameCache: JSON.parse(fs.readFileSync(cacheFileName, "utf8")) +}; +fs.writeFileSync("part1.js", UglifyJS.minify({ + "file1.js": fs.readFileSync("file1.js", "utf8"), + "file2.js": fs.readFileSync("file2.js", "utf8") +}, options).code, "utf8"); +fs.writeFileSync("part2.js", UglifyJS.minify({ + "file3.js": fs.readFileSync("file3.js", "utf8"), + "file4.js": fs.readFileSync("file4.js", "utf8") +}, options).code, "utf8"); +fs.writeFileSync(cacheFileName, JSON.stringify(options.nameCache), "utf8"); +``` + +An example of a combination of `minify()` options: +```javascript +var code = { + "file1.js": "function add(first, second) { return first + second; }", + "file2.js": "console.log(add(1 + 2, 3 + 4));" +}; +var options = { + toplevel: true, + compress: { + global_defs: { + "@console.log": "alert" + }, + passes: 2 + }, + output: { + beautify: false, + preamble: "/* uglified */" + } +}; +var result = UglifyJS.minify(code, options); +console.log(result.code); +// /* uglified */ +// alert(10);" +``` + +To produce warnings: +```javascript +var code = "function f(){ var u; return 2 + 3; }"; +var options = { warnings: true }; +var result = UglifyJS.minify(code, options); +console.log(result.error); // runtime error, `undefined` in this case +console.log(result.warnings); // [ 'Dropping unused variable u [0:1,18]' ] +console.log(result.code); // function f(){return 5} +``` + +An error example: +```javascript +var result = UglifyJS.minify({"foo.js" : "if (0) else console.log(1);"}); +console.log(JSON.stringify(result.error)); +// {"message":"Unexpected token: keyword (else)","filename":"foo.js","line":1,"col":7,"pos":7} +``` +Note: unlike `uglify-js@2.x`, the `3.x` API does not throw errors. To +achieve a similar effect one could do the following: +```javascript +var result = UglifyJS.minify(code, options); +if (result.error) throw result.error; +``` + +## Minify options + +- `warnings` (default `false`) — pass `true` to return compressor warnings + in `result.warnings`. Use the value `"verbose"` for more detailed warnings. + +- `parse` (default `{}`) — pass an object if you wish to specify some + additional [parse options](#parse-options). + +- `compress` (default `{}`) — pass `false` to skip compressing entirely. + Pass an object to specify custom [compress options](#compress-options). + +- `mangle` (default `true`) — pass `false` to skip mangling names, or pass + an object to specify [mangle options](#mangle-options) (see below). + + - `mangle.properties` (default `false`) — a subcategory of the mangle option. + Pass an object to specify custom [mangle property options](#mangle-properties-options). + +- `output` (default `null`) — pass an object if you wish to specify + additional [output options](#output-options). The defaults are optimized + for best compression. + +- `sourceMap` (default `false`) - pass an object if you wish to specify + [source map options](#source-map-options). + +- `toplevel` (default `false`) - set to `true` if you wish to enable top level + variable and function name mangling and to drop unused variables and functions. + +- `nameCache` (default `null`) - pass an empty object `{}` or a previously + used `nameCache` object if you wish to cache mangled variable and + property names across multiple invocations of `minify()`. Note: this is + a read/write property. `minify()` will read the name cache state of this + object and update it during minification so that it may be + reused or externally persisted by the user. + +- `ie8` (default `false`) - set to `true` to support IE8. + +## Minify options structure + +```javascript +{ + warnings: false, + parse: { + // parse options + }, + compress: { + // compress options + }, + mangle: { + // mangle options + + properties: { + // mangle property options + } + }, + output: { + // output options + }, + sourceMap: { + // source map options + }, + nameCache: null, // or specify a name cache object + toplevel: false, + ie8: false, +} +``` + +### Source map options + +To generate a source map: +```javascript +var result = UglifyJS.minify({"file1.js": "var a = function() {};"}, { + sourceMap: { + filename: "out.js", + url: "out.js.map" + } +}); +console.log(result.code); // minified output +console.log(result.map); // source map +``` + +Note that the source map is not saved in a file, it's just returned in +`result.map`. The value passed for `sourceMap.url` is only used to set +`//# sourceMappingURL=out.js.map` in `result.code`. The value of +`filename` is only used to set `file` attribute (see [the spec][sm-spec]) +in source map file. + +You can set option `sourceMap.url` to be `"inline"` and source map will +be appended to code. + +You can also specify sourceRoot property to be included in source map: +```javascript +var result = UglifyJS.minify({"file1.js": "var a = function() {};"}, { + sourceMap: { + root: "http://example.com/src", + url: "out.js.map" + } +}); +``` + +If you're compressing compiled JavaScript and have a source map for it, you +can use `sourceMap.content`: +```javascript +var result = UglifyJS.minify({"compiled.js": "compiled code"}, { + sourceMap: { + content: "content from compiled.js.map", + url: "minified.js.map" + } +}); +// same as before, it returns `code` and `map` +``` + +If you're using the `X-SourceMap` header instead, you can just omit `sourceMap.url`. + +## Parse options + +- `bare_returns` (default `false`) -- support top level `return` statements +- `html5_comments` (default `true`) +- `shebang` (default `true`) -- support `#!command` as the first line + +## Compress options - `sequences` (default: true) -- join consecutive simple statements using the comma operator. May be set to a positive integer to specify the maximum number @@ -347,6 +620,9 @@ to set `true`; it's effectively a shortcut for `foo=true`). comparison are switching. Compression only works if both `comparisons` and `unsafe_comps` are both set to true. +- `unsafe_Func` (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. @@ -368,6 +644,10 @@ to set `true`; it's effectively a shortcut for `foo=true`). - `booleans` -- various optimizations for boolean context, for example `!!a ? b : c → a ? b : c` +- `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. + - `loops` -- optimizations for `do`, `while` and `for` loops when we can statically determine the condition @@ -375,7 +655,7 @@ to set `true`; it's effectively a shortcut for `foo=true`). assignments do not count as references unless set to `"keep_assign"`) - `toplevel` -- drop unreferenced functions (`"funcs"`) and/or variables (`"vars"`) - in the toplevel scope (`false` by default, `true` to drop both unreferenced + in the top level scope (`false` by default, `true` to drop both unreferenced functions and variables) - `top_retain` -- prevent specific toplevel functions and variables from `unused` @@ -388,13 +668,15 @@ to set `true`; it's effectively a shortcut for `foo=true`). - `if_return` -- optimizations for if/return and if/continue +- `inline` -- embed simple functions + - `join_vars` -- join consecutive `var` statements - `cascade` -- small optimization for sequences, transform `x, x` into `x` and `x = something(), x` into `x = something()` -- `collapse_vars` -- Collapse single-use `var` and `const` definitions - when possible. +- `collapse_vars` -- Collapse single-use non-constant variables - side + effects permitting. - `reduce_vars` -- Improve optimization on variables assigned with and used as constant values. @@ -439,7 +721,7 @@ to set `true`; it's effectively a shortcut for `foo=true`). compressor from discarding function names. Useful for code relying on `Function.prototype.name`. See also: the `keep_fnames` [mangle option](#mangle). -- `passes` -- default `1`. Number of times to run compress with a maximum of 3. +- `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. @@ -451,122 +733,110 @@ to set `true`; it's effectively a shortcut for `foo=true`). annotation `/*@__PURE__*/` or `/*#__PURE__*/` immediately precedes the call. For example: `/*@__PURE__*/foo();` +## Mangle options -### The `unsafe` option +- `reserved` (default `[]`). Pass an array of identifiers that should be + excluded from mangling. Example: `["foo", "bar"]`. -It enables some transformations that *might* break code logic in certain -contrived cases, but should be fine for most code. You might want to try it -on your own code, it should reduce the minified size. Here's what happens -when this flag is on: +- `toplevel` (default `false`). Pass `true` to mangle names declared in the + top level scope. -- `new Array(1, 2, 3)` or `Array(1, 2, 3)` → `[ 1, 2, 3 ]` -- `new Object()` → `{}` -- `String(exp)` or `exp.toString()` → `"" + exp` -- `new Object/RegExp/Function/Error/Array (...)` → we discard the `new` -- `typeof foo == "undefined"` → `foo === void 0` -- `void 0` → `undefined` (if there is a variable named "undefined" in - scope; we do it because the variable name will be mangled, typically - reduced to a single character) +- `keep_fnames` (default `false`). Pass `true` to not mangle function names. + Useful for code relying on `Function.prototype.name`. See also: the `keep_fnames` + [compress option](#compress-options). -### Conditional compilation +- `eval` (default `false`). Pass `true` to mangle names visible in scopes + where `eval` or `with` are used. + +Examples: -You can use the `--define` (`-d`) switch in order to declare global -variables that UglifyJS will assume to be constants (unless defined in -scope). For example if you pass `--define DEBUG=false` then, coupled with -dead code removal UglifyJS will discard the following from the output: ```javascript -if (DEBUG) { - console.log("debug stuff"); +// test.js +var globalVar; +function funcName(firstLongName, anotherLongName) { + var myVariable = firstLongName + anotherLongName; } ``` - -You can specify nested constants in the form of `--define env.DEBUG=false`. - -UglifyJS will warn about the condition being always false and about dropping -unreachable code; for now there is no option to turn off only this specific -warning, you can pass `warnings=false` to turn off *all* warnings. - -Another way of doing that is to declare your globals as constants in a -separate file and include it into the build. For example you can have a -`build/defines.js` file with the following: ```javascript -const DEBUG = false; -const PRODUCTION = true; -// etc. -``` - -and build your code like this: +var code = fs.readFileSync("test.js", "utf8"); - uglifyjs build/defines.js js/foo.js js/bar.js... -c +UglifyJS.minify(code).code; +// 'function funcName(a,n){}var globalVar;' -UglifyJS will notice the constants and, since they cannot be altered, it -will evaluate references to them to the value itself and drop unreachable -code as usual. The build will contain the `const` declarations if you use -them. If you are targeting < ES6 environments which does not support `const`, -using `var` with `reduce_vars` (enabled by default) should suffice. +UglifyJS.minify(code, { mangle: { reserved: ['firstLongName'] } }).code; +// 'function funcName(firstLongName,a){}var globalVar;' -<a name="codegen-options"></a> +UglifyJS.minify(code, { mangle: { toplevel: true } }).code; +// 'function n(n,a){}var a;' +``` -#### Conditional compilation, API -You can also use conditional compilation via the programmatic API. With the difference that the -property name is `global_defs` and is a compressor property: +### Mangle properties options -```js -uglifyJS.minify([ "input.js"], { - compress: { - dead_code: true, - global_defs: { - DEBUG: false - } - } -}); -``` +- `reserved` (default: `[]`) -- Do not mangle property names listed in the + `reserved` array. +- `regex` (default: `null`) -— Pass a RegExp literal to only mangle property + names matching the regular expression. +- `keep_quoted` (default: `false`) -— Only mangle unquoted property names. +- `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. +- `builtins` (default: `false`) -- Use `true` to allow the mangling of builtin + DOM properties. Not recommended to override this setting. -## Beautifier options +## Output options The code generator tries to output shortest code possible by default. In case you want beautified output, pass `--beautify` (`-b`). Optionally you can pass additional arguments that control the code output: +- `ascii_only` (default `false`) -- escape Unicode characters in strings and + regexps (affects directives with non-ascii characters becoming invalid) - `beautify` (default `true`) -- whether to actually beautify the output. Passing `-b` will set this to true, but you might need to pass `-b` even when you want to generate minified code, in order to specify additional arguments, so you can use `-b beautify=false` to override it. -- `indent-level` (default 4) -- `indent-start` (default 0) -- prefix all lines by that many spaces -- `quote-keys` (default `false`) -- pass `true` to quote all keys in literal - objects -- `space-colon` (default `true`) -- insert a space after the colon signs -- `ascii-only` (default `false`) -- escape Unicode characters in strings and - regexps (affects directives with non-ascii characters becoming invalid) -- `inline-script` (default `false`) -- escape the slash in occurrences of - `</script` in strings -- `width` (default 80) -- only takes effect when beautification is on, this - specifies an (orientative) line width that the beautifier will try to - obey. It refers to the width of the line text (excluding indentation). - It doesn't work very well currently, but it does make the code generated - by UglifyJS more readable. -- `max-line-len` (default 32000) -- maximum line length (for uglified code) - `bracketize` (default `false`) -- always insert brackets in `if`, `for`, `do`, `while` or `with` statements, even if their body is a single statement. -- `semicolons` (default `true`) -- separate statements with semicolons. If - you pass `false` then whenever possible we will use a newline instead of a - semicolon, leading to more readable output of uglified code (size before - gzip could be smaller; size after gzip insignificantly larger). +- `comments` (default `false`) -- pass `true` or `"all"` to preserve all + comments, `"some"` to preserve some comments, a regular expression string + (e.g. `/^!/`) or a function. +- `indent_level` (default 4) +- `indent_start` (default 0) -- prefix all lines by that many spaces +- `inline_script` (default `false`) -- escape the slash in occurrences of + `</script` in strings +- `keep_quoted_props` (default `false`) -- when turned on, prevents stripping + quotes from property names in object literals. +- `max_line_len` (default `false`) -- maximum line length (for uglified code) - `preamble` (default `null`) -- when passed it must be a string and it will be prepended to the output literally. The source map will adjust for this text. Can be used to insert a comment containing licensing information, for example. +- `preserve_line` (default `false`) -- pass `true` to preserve lines, but it + only works if `beautify` is set to `false`. +- `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. + 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 -- `keep_quoted_props` (default `false`) -- when turned on, prevents stripping - quotes from property names in object literals. +- `semicolons` (default `true`) -- separate statements with semicolons. If + you pass `false` then whenever possible we will use a newline instead of a + semicolon, leading to more readable output of uglified code (size before + gzip could be smaller; size after gzip insignificantly larger). +- `shebang` (default `true`) -- preserve shebang `#!` in preamble (bash scripts) +- `width` (default 80) -- only takes effect when beautification is on, this + specifies an (orientative) line width that the beautifier will try to + obey. It refers to the width of the line text (excluding indentation). + It doesn't work very well currently, but it does make the code generated + by UglifyJS more readable. +- `wrap_iife` (default `false`) -- pass `true` to wrap immediately invoked + function expressions. See + [#640](https://github.com/mishoo/UglifyJS2/issues/640) for more details. + +# Miscellaneous ### Keeping copyright notices or other comments @@ -574,18 +844,18 @@ You can pass `--comments` to retain certain comments in the output. By default it will keep JSDoc-style comments that contain "@preserve", "@license" or "@cc_on" (conditional compilation for IE). You can pass `--comments all` to keep all the comments, or a valid JavaScript regexp to -keep only comments that match this regexp. For example `--comments -'/foo|bar/'` will keep only comments that contain "foo" or "bar". +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(); + /** @preserve Foo Bar */ + function g() { + // this function is never called + } + return something(); } ``` @@ -596,400 +866,193 @@ discarded by the compressor as not referenced. The safest comments where to place copyright information (or other info that needs to be kept in the output) are comments attached to toplevel nodes. -## Support for the SpiderMonkey AST - -UglifyJS2 has its own abstract syntax tree format; for -[practical reasons](http://lisperator.net/blog/uglifyjs-why-not-switching-to-spidermonkey-ast/) -we can't easily change to using the SpiderMonkey AST internally. However, -UglifyJS now has a converter which can import a SpiderMonkey AST. +### The `unsafe` `compress` option -For example [Acorn][acorn] is a super-fast parser that produces a -SpiderMonkey AST. It has a small CLI utility that parses one file and dumps -the AST in JSON on the standard output. To use UglifyJS to mangle and -compress that: - - acorn file.js | uglifyjs --spidermonkey -m -c - -The `--spidermonkey` option tells UglifyJS that all input files are not -JavaScript, but JS code described in SpiderMonkey AST in JSON. Therefore we -don't use our own parser in this case, but just transform that AST into our -internal AST. - -### Use Acorn for parsing - -More for fun, I added the `--acorn` option which will use Acorn to do all -the parsing. If you pass this option, UglifyJS will `require("acorn")`. - -Acorn is really fast (e.g. 250ms instead of 380ms on some 650K code), but -converting the SpiderMonkey tree that Acorn produces takes another 150ms so -in total it's a bit more than just using UglifyJS's own parser. - -### Using UglifyJS to transform SpiderMonkey AST +It enables some transformations that *might* break code logic in certain +contrived cases, but should be fine for most code. You might want to try it +on your own code, it should reduce the minified size. Here's what happens +when this flag is on: -Now you can use UglifyJS as any other intermediate tool for transforming -JavaScript ASTs in SpiderMonkey format. +- `new Array(1, 2, 3)` or `Array(1, 2, 3)` → `[ 1, 2, 3 ]` +- `new Object()` → `{}` +- `String(exp)` or `exp.toString()` → `"" + exp` +- `new Object/RegExp/Function/Error/Array (...)` → we discard the `new` +- `void 0` → `undefined` (if there is a variable named "undefined" in + scope; we do it because the variable name will be mangled, typically + reduced to a single character) -Example: +### Conditional compilation +You can use the `--define` (`-d`) switch in order to declare global +variables that UglifyJS will assume to be constants (unless defined in +scope). For example if you pass `--define DEBUG=false` then, coupled with +dead code removal UglifyJS will discard the following from the output: ```javascript -function uglify(ast, options, mangle) { - // Conversion from SpiderMonkey AST to internal format - var uAST = UglifyJS.AST_Node.from_mozilla_ast(ast); - - // Compression - uAST.figure_out_scope(); - uAST = UglifyJS.Compressor(options).compress(uAST); - - // Mangling (optional) - if (mangle) { - uAST.figure_out_scope(); - uAST.compute_char_frequency(); - uAST.mangle_names(); - } - - // Back-conversion to SpiderMonkey AST - return uAST.to_mozilla_ast(); +if (DEBUG) { + console.log("debug stuff"); } ``` -Check out -[original blog post](http://rreverser.com/using-mozilla-ast-with-uglifyjs/) -for details. - -API Reference -------------- - -Assuming installation via NPM, you can load UglifyJS in your application -like this: -```javascript -var UglifyJS = require("uglify-js"); -``` - -It exports a lot of names, but I'll discuss here the basics that are needed -for parsing, mangling and compressing a piece of code. The sequence is (1) -parse, (2) compress, (3) mangle, (4) generate output code. - -### The simple way +You can specify nested constants in the form of `--define env.DEBUG=false`. -There's a single toplevel function which combines all the steps. If you -don't need additional customization, you might want to go with `minify`. -Example: -```javascript -var result = UglifyJS.minify("/path/to/file.js"); -console.log(result.code); // minified output -// if you need to pass code instead of file name -var result = UglifyJS.minify("var b = function () {};", {fromString: true}); -``` +UglifyJS will warn about the condition being always false and about dropping +unreachable code; for now there is no option to turn off only this specific +warning, you can pass `warnings=false` to turn off *all* warnings. -You can also compress multiple files: +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 result = UglifyJS.minify([ "file1.js", "file2.js", "file3.js" ]); -console.log(result.code); +var DEBUG = false; +var PRODUCTION = true; +// etc. ``` -To generate a source map: -```javascript -var result = UglifyJS.minify([ "file1.js", "file2.js", "file3.js" ], { - outSourceMap: "out.js.map" -}); -console.log(result.code); // minified output -console.log(result.map); -``` +and build your code like this: -To generate a source map with the fromString option, you can also use an object: -```javascript -var result = UglifyJS.minify({"file1.js": "var a = function () {};"}, { - outSourceMap: "out.js.map", - outFileName: "out.js", - fromString: true -}); -``` + uglifyjs build/defines.js js/foo.js js/bar.js... -c -Note that the source map is not saved in a file, it's just returned in -`result.map`. The value passed for `outSourceMap` is only used to set -`//# sourceMappingURL=out.js.map` in `result.code`. The value of -`outFileName` is only used to set `file` attribute in source map file. +UglifyJS will notice the constants and, since they cannot be altered, it +will evaluate references to them to the value itself and drop unreachable +code as usual. The build will contain the `const` declarations if you use +them. If you are targeting < ES6 environments which does not support `const`, +using `var` with `reduce_vars` (enabled by default) should suffice. -The `file` attribute in the source map (see [the spec][sm-spec]) will -use `outFileName` firstly, if it's falsy, then will be deduced from -`outSourceMap` (by removing `'.map'`). +### Conditional compilation API -You can set option `sourceMapInline` to be `true` and source map will -be appended to code. +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: -You can also specify sourceRoot property to be included in source map: ```javascript -var result = UglifyJS.minify([ "file1.js", "file2.js", "file3.js" ], { - outSourceMap: "out.js.map", - sourceRoot: "http://example.com/src" +var result = UglifyJS.minify(fs.readFileSync("input.js", "utf8"), { + compress: { + dead_code: true, + global_defs: { + DEBUG: false + } + } }); ``` -If you're compressing compiled JavaScript and have a source map for it, you -can use the `inSourceMap` argument: +To replace an identifier with an arbitrary non-constant expression it is +necessary to prefix the `global_defs` key with `"@"` to instruct UglifyJS +to parse the value as an expression: ```javascript -var result = UglifyJS.minify("compiled.js", { - inSourceMap: "compiled.js.map", - outSourceMap: "minified.js.map" -}); -// same as before, it returns `code` and `map` +UglifyJS.minify("alert('hello');", { + compress: { + global_defs: { + "@alert": "console.log" + } + } +}).code; +// returns: 'console.log("hello");' ``` -If your input source map is not in a file, you can pass it in as an object -using the `inSourceMap` argument: - +Otherwise it would be replaced as string literal: ```javascript -var result = UglifyJS.minify("compiled.js", { - inSourceMap: JSON.parse(my_source_map_string), - outSourceMap: "minified.js.map" -}); +UglifyJS.minify("alert('hello');", { + compress: { + global_defs: { + "alert": "console.log" + } + } +}).code; +// returns: '"console.log"("hello");' ``` -The `inSourceMap` is only used if you also request `outSourceMap` (it makes -no sense otherwise). - -To set the source map url, use the `sourceMapUrl` option. -If you're using the X-SourceMap header instead, you can just set the `sourceMapUrl` option to false. -Defaults to outSourceMap: - +### Using native Uglify AST with `minify()` ```javascript -var result = UglifyJS.minify([ "file1.js" ], { - outSourceMap: "out.js.map", - sourceMapUrl: "localhost/out.js.map" +// example: parse only, produce native Uglify AST + +var result = UglifyJS.minify(code, { + parse: {}, + compress: false, + mangle: false, + output: { + ast: true, + code: false // optional - faster if false + } }); -``` - -Other options: - -- `warnings` (default `false`) — pass `true` to display compressor warnings. - -- `fromString` (default `false`) — if you pass `true` then you can pass - JavaScript source code, rather than file names. - -- `mangle` (default `true`) — pass `false` to skip mangling names, or pass - an object to specify mangling options (see below). - -- `mangleProperties` (default `false`) — pass an object to specify custom - mangle property options. - -- `output` (default `null`) — pass an object if you wish to specify - additional [output options][codegen]. The defaults are optimized - for best compression. - -- `compress` (default `{}`) — pass `false` to skip compressing entirely. - Pass an object to specify custom [compressor options][compressor]. - -- `parse` (default {}) — pass an object if you wish to specify some - additional [parser options][parser]. (not all options available... see below) - -##### mangle - - - `except` - pass an array of identifiers that should be excluded from mangling - - - `toplevel` — mangle names declared in the toplevel scope (disabled by - default). - - - `eval` — mangle names visible in scopes where eval or with are used - (disabled by default). - - - `keep_fnames` -- default `false`. Pass `true` to not mangle - function names. Useful for code relying on `Function.prototype.name`. - See also: the `keep_fnames` [compress option](#compressor-options). - - Examples: - - ```javascript - //tst.js - var globalVar; - function funcName(firstLongName, anotherLongName) - { - var myVariable = firstLongName + anotherLongName; - } - - UglifyJS.minify("tst.js").code; - // 'function funcName(a,n){}var globalVar;' - - UglifyJS.minify("tst.js", { mangle: { except: ['firstLongName'] } }).code; - // 'function funcName(firstLongName,a){}var globalVar;' - - UglifyJS.minify("tst.js", { mangle: { toplevel: true } }).code; - // 'function n(n,a){}var a;' - ``` -##### mangleProperties options - - - `regex` — Pass a RegExp to only mangle certain names (maps to the `--mangle-regex` CLI arguments option) - - `ignore_quoted` – Only mangle unquoted property names (maps to the `--mangle-props 2` CLI arguments option) - - `debug` – Mangle names with the original name still present (maps to the `--mangle-props-debug` CLI arguments option). Defaults to `false`. Pass an empty string to enable, or a non-empty string to set the suffix. - -We could add more options to `UglifyJS.minify` — if you need additional -functionality please suggest! - -### The hard way - -Following there's more detailed API info, in case the `minify` function is -too simple for your needs. - -#### The parser -```javascript -var toplevel_ast = UglifyJS.parse(code, options); +// result.ast contains native Uglify AST ``` - -`options` is optional and if present it must be an object. The following -properties are available: - -- `strict` — disable automatic semicolon insertion and support for trailing - comma in arrays and objects -- `bare_returns` — Allow return outside of functions. (maps to the - `--bare-returns` CLI arguments option and available to `minify` `parse` - other options object) -- `filename` — the name of the file where this code is coming from -- `toplevel` — a `toplevel` node (as returned by a previous invocation of - `parse`) - -The last two options are useful when you'd like to minify multiple files and -get a single file as the output and a proper source map. Our CLI tool does -something like this: ```javascript -var toplevel = null; -files.forEach(function(file){ - var code = fs.readFileSync(file, "utf8"); - toplevel = UglifyJS.parse(code, { - filename: file, - toplevel: toplevel - }); +// example: accept native Uglify AST input and then compress and mangle +// to produce both code and native AST. + +var result = UglifyJS.minify(ast, { + compress: {}, + mangle: {}, + output: { + ast: true, + code: true // optional - faster if false + } }); -``` - -After this, we have in `toplevel` a big AST containing all our files, with -each token having proper information about where it came from. - -#### Scope information -UglifyJS contains a scope analyzer that you need to call manually before -compressing or mangling. Basically it augments various nodes in the AST -with information about where is a name defined, how many times is a name -referenced, if it is a global or not, if a function is using `eval` or the -`with` statement etc. I will discuss this some place else, for now what's -important to know is that you need to call the following before doing -anything with the tree: -```javascript -toplevel.figure_out_scope() +// result.ast contains native Uglify AST +// result.code contains the minified code in string form. ``` -#### Compression - -Like this: -```javascript -var compressor = UglifyJS.Compressor(options); -var compressed_ast = compressor.compress(toplevel); -``` +### Working with Uglify AST -The `options` can be missing. Available options are discussed above in -“Compressor options”. Defaults should lead to best compression in most -scripts. +Transversal and transformation of the native AST can be performed through +[`TreeWalker`](http://lisperator.net/uglifyjs/walk) and +[`TreeTransformer`](http://lisperator.net/uglifyjs/transform) respectively. -The compressor is destructive, so don't rely that `toplevel` remains the -original tree. +### ESTree / SpiderMonkey AST -#### Mangling - -After compression it is a good idea to call again `figure_out_scope` (since -the compressor might drop unused variables / unreachable code and this might -change the number of identifiers or their position). Optionally, you can -call a trick that helps after Gzip (counting character frequency in -non-mangleable words). Example: -```javascript -compressed_ast.figure_out_scope(); -compressed_ast.compute_char_frequency(); -compressed_ast.mangle_names(); -``` - -#### Generating output - -AST nodes have a `print` method that takes an output stream. Essentially, -to generate code you do this: -```javascript -var stream = UglifyJS.OutputStream(options); -compressed_ast.print(stream); -var code = stream.toString(); // this is your minified code -``` +UglifyJS has its own abstract syntax tree format; for +[practical reasons](http://lisperator.net/blog/uglifyjs-why-not-switching-to-spidermonkey-ast/) +we can't easily change to using the SpiderMonkey AST internally. However, +UglifyJS now has a converter which can import a SpiderMonkey AST. -or, for a shortcut you can do: -```javascript -var code = compressed_ast.print_to_string(options); -``` +For example [Acorn][acorn] is a super-fast parser that produces a +SpiderMonkey AST. It has a small CLI utility that parses one file and dumps +the AST in JSON on the standard output. To use UglifyJS to mangle and +compress that: -As usual, `options` is optional. The output stream accepts a lot of options, -most of them documented above in section “Beautifier options”. The two -which we care about here are `source_map` and `comments`. + acorn file.js | uglifyjs -p spidermonkey -m -c -#### Keeping comments in the output +The `-p spidermonkey` option tells UglifyJS that all input files are not +JavaScript, but JS code described in SpiderMonkey AST in JSON. Therefore we +don't use our own parser in this case, but just transform that AST into our +internal AST. -In order to keep certain comments in the output you need to pass the -`comments` option. Pass a RegExp (as string starting and closing with `/` -or pass a RegExp object), a boolean or a function. Stringified options -`all` and `some` can be passed too, where `some` behaves like it's cli -equivalent `--comments` without passing a value. If you pass a RegExp, -only those comments whose body matches the RegExp will be kept. Note that body -means without the initial `//` or `/*`. If you pass a function, it will be -called for every comment in the tree and will receive two arguments: the -node that the comment is attached to, and the comment token itself. +### Use Acorn for parsing -The comment token has these properties: +More for fun, I added the `-p acorn` option which will use Acorn to do all +the parsing. If you pass this option, UglifyJS will `require("acorn")`. -- `type`: "comment1" for single-line comments or "comment2" for multi-line - comments -- `value`: the comment body -- `pos` and `endpos`: the start/end positions (zero-based indexes) in the - original code where this comment appears -- `line` and `col`: the line and column where this comment appears in the - original code -- `file` — the file name of the original file -- `nlb` — true if there was a newline before this comment in the original - code, or if this comment contains a newline. +Acorn is really fast (e.g. 250ms instead of 380ms on some 650K code), but +converting the SpiderMonkey tree that Acorn produces takes another 150ms so +in total it's a bit more than just using UglifyJS's own parser. -Your function should return `true` to keep the comment, or a falsy value -otherwise. +[acorn]: https://github.com/ternjs/acorn +[sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k -#### Generating a source mapping +### Uglify Fast Minify Mode -You need to pass the `source_map` argument when calling `print`. It needs -to be a `SourceMap` object (which is a thin wrapper on top of the -[source-map][source-map] library). +It's not well known, but whitespace removal and symbol mangling accounts +for 95% of the size reduction in minified code for most javascript - not +elaborate code transforms. One can simply disable `compress` to speed up +Uglify builds by 3 to 4 times. In this fast `mangle`-only mode Uglify has +comparable minify speeds and gzip sizes to +[`butternut`](https://www.npmjs.com/package/butternut): -Example: -```javascript -var source_map = UglifyJS.SourceMap(source_map_options); -var stream = UglifyJS.OutputStream({ - ... - source_map: source_map -}); -compressed_ast.print(stream); +| d3.js | minify size | gzip size | minify time (seconds) | +| --- | ---: | ---: | ---: | +| original | 451,131 | 108,733 | - | +| uglify-js@3.0.24 mangle=false, compress=false | 316,600 | 85,245 | 0.70 | +| uglify-js@3.0.24 mangle=true, compress=false | 220,216 | 72,730 | 1.13 | +| butternut@0.4.6 | 217,568 | 72,738 | 1.41 | +| uglify-js@3.0.24 mangle=true, compress=true | 212,511 | 71,560 | 3.36 | +| babili@0.1.4 | 210,713 | 72,140 | 12.64 | -var code = stream.toString(); -var map = source_map.toString(); // json output for your source map +To enable fast minify mode from the CLI use: +``` +uglifyjs file.js -m +``` +To enable fast minify mode with the API use: +```js +UglifyJS.minify(code, { compress: false, mangle: true }); ``` - -The `source_map_options` (optional) can contain the following properties: - -- `file`: the name of the JavaScript output file that this mapping refers to -- `root`: the `sourceRoot` property (see the [spec][sm-spec]) -- `orig`: the "original source map", handy when you compress generated JS - and want to map the minified output back to the original code where it - came from. It can be simply a string in JSON, or a JSON object containing - the original source map. - - [acorn]: https://github.com/ternjs/acorn - [source-map]: https://github.com/mozilla/source-map - [sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit - [codegen]: http://lisperator.net/uglifyjs/codegen - [compressor]: http://lisperator.net/uglifyjs/compress - [parser]: http://lisperator.net/uglifyjs/parser - -#### Support for `const` - -`const` in `uglify-js@2.x` has function scope and as such behaves much like -`var` - unlike `const` in ES2015 (ES6) which has block scope. It is recommended -to avoid using `const` for this reason as it will have undefined behavior when -run on an ES2015 compatible browser. |