minify

package module
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 Go to latest Published: Oct 24, 2024 License: MIT Imports: 18 Imported by: 387

README

Minify API reference Go Report Card codecov

Online demo if you need to minify files now.

Binaries of CLI for various platforms. See CLI for more installation instructions.

Windows binary from scoop install with scoop install main/minify

Python bindings install with pip install tdewolff-minify

JavaScript bindings install with npm i @tdewolff/minify

.NET bindings install with Install-Package NMinify or dotnet add package NMinify, thanks to Jonas Kamsker for the port

Did you know that the shortest valid piece of HTML5 is <!doctype html><title>x</title>? See for yourself at the W3C Validator!

Minify is a minifier package written in Go. It provides HTML5, CSS3, JS, JSON, SVG and XML minifiers and an interface to implement any other minifier. Minification is the process of removing bytes from a file (such as whitespace) without changing its output and therefore shrinking its size and speeding up transmission over the internet and possibly parsing. The implemented minifiers are designed for high performance (see https://github.com/privatenumber/minification-benchmarks where this library is (one of) the fastest JS minifiers).

The core functionality associates mimetypes with minification functions, allowing embedded resources (like CSS or JS within HTML files) to be minified as well. Users can add new implementations that are triggered based on a mimetype (or pattern), or redirect to an external command (like ClosureCompiler, UglifyCSS, ...).

Sponsors

I'm actively looking for support in the form of donations or sponsorships to keep developing this library and highly appreciate any gesture. Please see the Sponsors button in GitHub for ways to contribute, or contact me directly.

SiteGround

Table of Contents
Roadmap
  • Use ASM/SSE to further speed-up core parts of the parsers/minifiers
  • Improve JS minifiers by shortening variables and proper semicolon omission
  • Speed-up SVG minifier, it is very slow
  • Proper parser error reporting and line number + column information
  • Generation of source maps (uncertain, might slow down parsers too much if it cannot run separately nicely)
  • Create a cmd to pack webfiles (much like webpack), ie. merging CSS and JS files, inlining small external files, minification and gzipping. This would work on HTML files.

Prologue

Minifiers or bindings to minifiers exist in almost all programming languages. Some implementations are merely using several regular expressions to trim whitespace and comments (even though regex for parsing HTML/XML is ill-advised, for a good read see Regular Expressions: Now You Have Two Problems). Some implementations are much more profound, such as the YUI Compressor and Google Closure Compiler for JS. As most existing implementations either use JavaScript, use regexes, and don't focus on performance, they are pretty slow.

This minifier proves to be that fast and extensive minifier that can handle HTML and any other filetype it may contain (CSS, JS, ...). It is usually orders of magnitude faster than existing minifiers.

Installation

Make sure you have Git and Go (1.18 or higher) installed, run

mkdir Project
cd Project
go mod init
go get -u github.com/tdewolff/minify/v2

Then add the following imports to be able to use the various minifiers

import (
	"github.com/tdewolff/minify/v2"
	"github.com/tdewolff/minify/v2/css"
	"github.com/tdewolff/minify/v2/html"
	"github.com/tdewolff/minify/v2/js"
	"github.com/tdewolff/minify/v2/json"
	"github.com/tdewolff/minify/v2/svg"
	"github.com/tdewolff/minify/v2/xml"
)

You can optionally run go mod tidy to clean up the go.mod and go.sum files.

See CLI tool for installation instructions of the binary.

Docker

If you want to use Docker, please see https://hub.docker.com/r/tdewolff/minify.

$ docker run -it tdewolff/minify --help

API stability

There is no guarantee for absolute stability, but I take issues and bugs seriously and don't take API changes lightly. The library will be maintained in a compatible way unless vital bugs prevent me from doing so. There has been one API change after v1 which added options support and I took the opportunity to push through some more API clean up as well. There are no plans whatsoever for future API changes.

Testing

For all subpackages and the imported parse package, test coverage of 100% is pursued. Besides full coverage, the minifiers are fuzz tested using github.com/dvyukov/go-fuzz, see the wiki for the most important bugs found by fuzz testing. These tests ensure that everything works as intended and that the code does not crash (whatever the input). If you still encounter a bug, please file a bug report!

Performance

The benchmarks directory contains a number of standardized samples used to compare performance between changes. To give an indication of the speed of this library, I've ran the tests on my Thinkpad T460 (i5-6300U quad-core 2.4GHz running Arch Linux) using Go 1.15.

name                              time/op
CSS/sample_bootstrap.css-4          2.70ms ± 0%
CSS/sample_gumby.css-4              3.57ms ± 0%
CSS/sample_fontawesome.css-4         767µs ± 0%
CSS/sample_normalize.css-4          85.5µs ± 0%
HTML/sample_amazon.html-4           15.2ms ± 0%
HTML/sample_bbc.html-4              3.90ms ± 0%
HTML/sample_blogpost.html-4          420µs ± 0%
HTML/sample_es6.html-4              15.6ms ± 0%
HTML/sample_stackoverflow.html-4    3.73ms ± 0%
HTML/sample_wikipedia.html-4        6.60ms ± 0%
JS/sample_ace.js-4                  28.7ms ± 0%
JS/sample_dot.js-4                   357µs ± 0%
JS/sample_jquery.js-4               10.0ms ± 0%
JS/sample_jqueryui.js-4             20.4ms ± 0%
JS/sample_moment.js-4               3.47ms ± 0%
JSON/sample_large.json-4            3.25ms ± 0%
JSON/sample_testsuite.json-4        1.74ms ± 0%
JSON/sample_twitter.json-4          24.2µs ± 0%
SVG/sample_arctic.svg-4             34.7ms ± 0%
SVG/sample_gopher.svg-4              307µs ± 0%
SVG/sample_usa.svg-4                57.4ms ± 0%
SVG/sample_car.svg-4                18.0ms ± 0%
SVG/sample_tiger.svg-4              5.61ms ± 0%
XML/sample_books.xml-4              54.7µs ± 0%
XML/sample_catalog.xml-4            33.0µs ± 0%
XML/sample_omg.xml-4                7.17ms ± 0%

name                              speed
CSS/sample_bootstrap.css-4        50.7MB/s ± 0%
CSS/sample_gumby.css-4            52.1MB/s ± 0%
CSS/sample_fontawesome.css-4      61.2MB/s ± 0%
CSS/sample_normalize.css-4        70.8MB/s ± 0%
HTML/sample_amazon.html-4         31.1MB/s ± 0%
HTML/sample_bbc.html-4            29.5MB/s ± 0%
HTML/sample_blogpost.html-4       49.8MB/s ± 0%
HTML/sample_es6.html-4            65.6MB/s ± 0%
HTML/sample_stackoverflow.html-4  55.0MB/s ± 0%
HTML/sample_wikipedia.html-4      67.5MB/s ± 0%
JS/sample_ace.js-4                22.4MB/s ± 0%
JS/sample_dot.js-4                14.5MB/s ± 0%
JS/sample_jquery.js-4             24.8MB/s ± 0%
JS/sample_jqueryui.js-4           23.0MB/s ± 0%
JS/sample_moment.js-4             28.6MB/s ± 0%
JSON/sample_large.json-4           234MB/s ± 0%
JSON/sample_testsuite.json-4       394MB/s ± 0%
JSON/sample_twitter.json-4        63.0MB/s ± 0%
SVG/sample_arctic.svg-4           42.4MB/s ± 0%
SVG/sample_gopher.svg-4           19.0MB/s ± 0%
SVG/sample_usa.svg-4              17.8MB/s ± 0%
SVG/sample_car.svg-4              29.3MB/s ± 0%
SVG/sample_tiger.svg-4            12.2MB/s ± 0%
XML/sample_books.xml-4            81.0MB/s ± 0%
XML/sample_catalog.xml-4          58.6MB/s ± 0%
XML/sample_omg.xml-4               159MB/s ± 0%

HTML

HTML (with JS and CSS) minification typically shaves off about 10%.

The HTML5 minifier uses these minifications:

  • strip unnecessary whitespace and otherwise collapse it to one space (or newline if it originally contained a newline)
  • strip superfluous quotes, or uses single/double quotes whichever requires fewer escapes
  • strip default attribute values and attribute boolean values
  • strip some empty attributes
  • strip unrequired tags (html, head, body, ...)
  • strip unrequired end tags (tr, td, li, ... and often p)
  • strip default protocols (http:, https: and javascript:)
  • strip all comments (including conditional comments, old IE versions are not supported anymore by Microsoft)
  • shorten doctype and meta charset
  • lowercase tags, attributes and some values to enhance gzip compression

Options:

  • KeepSpecialComments preserve all special comments, including Server Side Includes such as <!--#include file="header.html" --> and IE conditional comments such as <!--[if IE 6]><![endif]--> and <![if IE 6]><![endif]>, see https://msdn.microsoft.com/en-us/library/ms537512(v=vs.85).aspx#syntax
  • KeepDefaultAttrVals preserve default attribute values such as <script type="application/javascript">
  • KeepDocumentTags preserve html, head and body tags
  • KeepEndTags preserve all end tags
  • KeepQuotes preserve quotes around attribute values
  • KeepWhitespace preserve whitespace between inline tags but still collapse multiple whitespace characters into one
  • TemplateDelims preserve context within and surrounding the given opening and closing delimiters

After recent benchmarking and profiling it became really fast and minifies pages in the 10ms range, making it viable for on-the-fly minification.

However, be careful when doing on-the-fly minification. Minification typically trims off 10% and does this at worst around about 20MB/s. This means users have to download slower than 2MB/s to make on-the-fly minification worthwhile. This may or may not apply in your situation. Rather use caching!

Whitespace removal

The whitespace removal mechanism collapses all sequences of whitespace (spaces, newlines, tabs) to a single space. If the sequence contained a newline or carriage return it will collapse into a newline character instead. It trims all text parts (in between tags) depending on whether it was preceded by a space from a previous piece of text and whether it is followed up by a block element or an inline element. In the former case we can omit spaces while for inline elements whitespace has significance.

Make sure your HTML doesn't depend on whitespace between block elements that have been changed to inline or inline-block elements using CSS. Your layout should not depend on those whitespaces as the minifier will remove them. An example is a menu consisting of multiple <li> that have display:inline-block applied and have whitespace in between them. It is bad practise to rely on whitespace for element positioning anyways!

CSS

Minification typically shaves off about 10%-15%. This CSS minifier will not do structural changes to your stylesheets. Although this could result in smaller files, the complexity is quite high and the risk of breaking website is high too.

The CSS minifier will only use safe minifications:

  • remove comments and unnecessary whitespace (but keep /*! ... */ which usually contains the license)
  • remove trailing semicolons
  • optimize margin, padding and border-width number of sides
  • shorten numbers by removing unnecessary + and zeros and rewriting with/without exponent
  • remove dimension and percentage for zero values
  • remove quotes for URLs
  • remove quotes for font families and make lowercase
  • rewrite hex colors to/from color names, or to three digit hex
  • rewrite rgb(, rgba(, hsl( and hsla( colors to hex or name
  • use four digit hex for alpha values (transparent → #0000)
  • replace normal and bold by numbers for font-weight and font
  • replace none → 0 for border, background and outline
  • lowercase all identifiers except classes, IDs and URLs to enhance gzip compression
  • shorten MS alpha function
  • rewrite data URIs with base64 or ASCII whichever is shorter
  • calls minifier for data URI mediatypes, thus you can compress embedded SVG files if you have that minifier attached
  • shorten aggregate declarations such as background and font

It does purposely not use the following techniques:

  • (partially) merge rulesets
  • (partially) split rulesets
  • collapse multiple declarations when main declaration is defined within a ruleset (don't put font-weight within an already existing font, too complex)
  • remove overwritten properties in ruleset (this not always overwrites it, for example with !important)
  • rewrite properties into one ruleset if possible (like margin-top, margin-right, margin-bottom and margin-left → margin)
  • put nested ID selector at the front (body > div#elem p → #elem p)
  • rewrite attribute selectors for IDs and classes (div[id=a] → div#a)
  • put space after pseudo-selectors (IE6 is old, move on!)

There are a couple of comparison tables online, such as CSS Minifier Comparison, CSS minifiers comparison and CleanCSS tests. Comparing speed between each, this minifier will usually be between 10x-300x faster than existing implementations, and even rank among the top for minification ratios. It falls short with the purposely not implemented and often unsafe techniques.

Options:

  • KeepCSS2 prohibits using CSS3 syntax (such as exponents in numbers, or rgba( → rgb(), might be incomplete
  • Precision number of significant digits to preserve for numbers, 0 means no trimming

JS

The JS minifier typically shaves off about 35% -- 65% of filesize depending on the file, which is a compression close to many other minifiers. Common speeds of PHP and JS implementations are about 100-300kB/s (see Uglify2, Adventures in PHP web asset minimization). This implementation is orders of magnitude faster at around ~25MB/s.

The following features are implemented:

  • remove superfluous whitespace
  • remove superfluous semicolons
  • shorten true, false, and undefined to !0, !1 and void 0
  • rename variables and functions to shorter names (not in global scope)
  • move var declarations to the top of the global/function scope (if more than one)
  • collapse if/else statements to expressions
  • minify conditional expressions to simpler ones
  • merge sequential expression statements to one, including into return and throw
  • remove superfluous grouping in expressions
  • shorten or remove string escapes
  • convert object key or index expression from string to identifier or decimal
  • merge concatenated strings
  • rewrite numbers (binary, octal, decimal, hexadecimal) to shorter representations

Options:

  • KeepVarNames keeps variable names as they are and omits shortening variable names
  • Precision number of significant digits to preserve for numbers, 0 means no trimming
  • Version ECMAScript version to use for output, 0 is the latest
Comparison with other tools

Performance is measured with time [command] ran 10 times and selecting the fastest one, on a Thinkpad T460 (i5-6300U quad-core 2.4GHz running Arch Linux) using Go 1.15.

  • minify: minify -o script.min.js script.js
  • esbuild: esbuild --minify --outfile=script.min.js script.js
  • terser: terser script.js --compress --mangle -o script.min.js
  • UglifyJS: uglifyjs --compress --mangle -o script.min.js script.js
  • Closure Compiler: closure-compiler -O SIMPLE --js script.js --js_output_file script.min.js --language_in ECMASCRIPT_NEXT -W QUIET --jscomp_off=checkVars optimization level SIMPLE instead of ADVANCED to make similar assumptions as do the other tools (do not rename/assume anything of global level variables)
Compression ratio (lower is better)

All tools give very similar results, although UglifyJS compresses slightly better.

Tool ace.js dot.js jquery.js jqueryui.js moment.js
minify 53.7% 64.8% 34.2% 51.3% 34.8%
esbuild 53.8% 66.3% 34.4% 53.1% 34.8%
terser 53.2% 65.2% 34.2% 51.8% 34.7%
UglifyJS 53.1% 64.7% 33.8% 50.7% 34.2%
Closure Compiler 53.4% 64.0% 35.7% 53.6% 34.3%
Time (lower is better)

Most tools are extremely slow, with minify and esbuild being orders of magnitudes faster.

Tool ace.js dot.js jquery.js jqueryui.js moment.js
minify 49ms 5ms 22ms 35ms 13ms
esbuild 64ms 9ms 31ms 51ms 17ms
terser 2900s 180ms 1400ms 2200ms 730ms
UglifyJS 3900ms 210ms 2000ms 3100ms 910ms
Closure Compiler 6100ms 2500ms 4400ms 5300ms 3500ms

JSON

Minification typically shaves off about 15% of filesize for common indented JSON such as generated by JSON Generator.

The JSON minifier only removes whitespace, which is the only thing that can be left out, and minifies numbers (1000 => 1e3).

Options:

  • Precision number of significant digits to preserve for numbers, 0 means no trimming
  • KeepNumbers do not minify numbers if set to true, by default numbers will be minified

SVG

The SVG minifier uses these minifications:

  • trim and collapse whitespace between all tags
  • strip comments, empty doctype, XML prelude, metadata
  • strip SVG version
  • strip CDATA sections wherever possible
  • collapse tags with no content to a void tag
  • minify style tag and attributes with the CSS minifier
  • minify colors
  • shorten lengths and numbers and remove default px unit
  • shorten path data
  • use relative or absolute positions in path data whichever is shorter

TODO:

  • convert attributes to style attribute whenever shorter
  • merge path data? (same style and no intersection -- the latter is difficult)

Options:

  • Precision number of significant digits to preserve for numbers, 0 means no trimming

XML

The XML minifier uses these minifications:

  • strip unnecessary whitespace and otherwise collapse it to one space (or newline if it originally contained a newline)
  • strip comments
  • collapse tags with no content to a void tag
  • strip CDATA sections wherever possible

Options:

  • KeepWhitespace preserve whitespace between inline tags but still collapse multiple whitespace characters into one

Usage

Any input stream is being buffered by the minification functions. This is how the underlying buffer package inherently works to ensure high performance. The output stream however is not buffered. It is wise to preallocate a buffer as big as the input to which the output is written, or otherwise use bufio to buffer to a streaming writer.

New

Retrieve a minifier struct which holds a map of mediatype → minifier functions.

m := minify.New()

The following loads all provided minifiers.

m := minify.New()
m.AddFunc("text/css", css.Minify)
m.AddFunc("text/html", html.Minify)
m.AddFunc("image/svg+xml", svg.Minify)
m.AddFuncRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"), js.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)

You can set options to several minifiers.

m.Add("text/html", &html.Minifier{
	KeepDefaultAttrVals: true,
	KeepWhitespace: true,
})
From reader

Minify from an io.Reader to an io.Writer for a specific mediatype.

if err := m.Minify(mediatype, w, r); err != nil {
	panic(err)
}
From bytes

Minify from and to a []byte for a specific mediatype.

b, err = m.Bytes(mediatype, b)
if err != nil {
	panic(err)
}
From string

Minify from and to a string for a specific mediatype.

s, err = m.String(mediatype, s)
if err != nil {
	panic(err)
}
To reader

Get a minifying reader for a specific mediatype.

mr := m.Reader(mediatype, r)
if _, err := mr.Read(b); err != nil {
	panic(err)
}
To writer

Get a minifying writer for a specific mediatype. Must be explicitly closed because it uses an io.Pipe underneath.

mw := m.Writer(mediatype, w)
if mw.Write([]byte("input")); err != nil {
	panic(err)
}
if err := mw.Close(); err != nil {
	panic(err)
}
Middleware

Minify resources on the fly using middleware. It passes a wrapped response writer to the handler that removes the Content-Length header. The minifier is chosen based on the Content-Type header or, if the header is empty, by the request URI file extension. This is on-the-fly processing, you should preferably cache the results though!

fs := http.FileServer(http.Dir("www/"))
http.Handle("/", m.Middleware(fs))
Custom minifier

Add a minifier for a specific mimetype.

type CustomMinifier struct {
	KeepLineBreaks bool
}

func (c *CustomMinifier) Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
	// ...
	return nil
}

m.Add(mimetype, &CustomMinifier{KeepLineBreaks: true})
// or
m.AddRegexp(regexp.MustCompile("/x-custom$"), &CustomMinifier{KeepLineBreaks: true})

Add a minify function for a specific mimetype.

m.AddFunc(mimetype, func(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
	// ...
	return nil
})
m.AddFuncRegexp(regexp.MustCompile("/x-custom$"), func(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
	// ...
	return nil
})

Add a command cmd with arguments args for a specific mimetype.

m.AddCmd(mimetype, exec.Command(cmd, args...))
m.AddCmdRegexp(regexp.MustCompile("/x-custom$"), exec.Command(cmd, args...))
Mediatypes

Using the params map[string]string argument one can pass parameters to the minifier such as seen in mediatypes (type/subtype; key1=val2; key2=val2). Examples are the encoding or charset of the data. Calling Minify will split the mimetype and parameters for the minifiers for you, but MinifyMimetype can be used if you already have them split up.

Minifiers can also be added using a regular expression. For example a minifier with image/.* will match any image mime.

Examples

Common minifiers

Basic example that minifies from stdin to stdout and loads the default HTML, CSS and JS minifiers. Optionally, one can enable java -jar build/compiler.jar to run for JS (for example the ClosureCompiler). Note that reading the file into a buffer first and writing to a pre-allocated buffer would be faster (but would disable streaming).

package main

import (
	"log"
	"os"
	"os/exec"

	"github.com/tdewolff/minify/v2"
	"github.com/tdewolff/minify/v2/css"
	"github.com/tdewolff/minify/v2/html"
	"github.com/tdewolff/minify/v2/js"
	"github.com/tdewolff/minify/v2/json"
	"github.com/tdewolff/minify/v2/svg"
	"github.com/tdewolff/minify/v2/xml"
)

func main() {
	m := minify.New()
	m.AddFunc("text/css", css.Minify)
	m.AddFunc("text/html", html.Minify)
	m.AddFunc("image/svg+xml", svg.Minify)
	m.AddFuncRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"), js.Minify)
	m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
	m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)

	if err := m.Minify("text/html", os.Stdout, os.Stdin); err != nil {
		panic(err)
	}
}
External minifiers

Below are some examples of using common external minifiers.

Closure Compiler

See Closure Compiler Application. Not tested.

m.AddCmdRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"),
    exec.Command("java", "-jar", "build/compiler.jar"))
UglifyJS

See UglifyJS.

m.AddCmdRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"),
    exec.Command("uglifyjs"))
esbuild

See esbuild.

m.AddCmdRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"),
    exec.Command("esbuild", "$in.js", "--minify", "--outfile=$out.js"))
Custom minifier

Custom minifier showing an example that implements the minifier function interface. Within a custom minifier, it is possible to call any minifier function (through m minify.Minifier) recursively when dealing with embedded resources.

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"strings"

	"github.com/tdewolff/minify/v2"
)

func main() {
	m := minify.New()
	m.AddFunc("text/plain", func(m *minify.M, w io.Writer, r io.Reader, _ map[string]string) error {
		// remove newlines and spaces
		rb := bufio.NewReader(r)
		for {
			line, err := rb.ReadString('\n')
			if err != nil && err != io.EOF {
				return err
			}
			if _, errws := io.WriteString(w, strings.Replace(line, " ", "", -1)); errws != nil {
				return errws
			}
			if err == io.EOF {
				break
			}
		}
		return nil
	})

	in := "Because my coffee was too cold, I heated it in the microwave."
	out, err := m.String("text/plain", in)
	if err != nil {
		panic(err)
	}
	fmt.Println(out)
	// Output: Becausemycoffeewastoocold,Iheateditinthemicrowave.
}
ResponseWriter
Middleware
func main() {
	m := minify.New()
	m.AddFunc("text/css", css.Minify)
	m.AddFunc("text/html", html.Minify)
	m.AddFunc("image/svg+xml", svg.Minify)
	m.AddFuncRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"), js.Minify)
	m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
	m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)

	fs := http.FileServer(http.Dir("www/"))
	http.Handle("/", m.MiddlewareWithError(fs))
}

func handleError(w http.ResponseWriter, r *http.Request, err error) {
    http.Error(w, err.Error(), http.StatusInternalServerError)
}

In order to properly handle minify errors, it is necessary to close the response writer since all writes are concurrently handled. There is no need to check errors on writes since they will be returned on closing.

func main() {
	m := minify.New()
	m.AddFunc("text/html", html.Minify)
	m.AddFuncRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"), js.Minify)

	input := `<script>const i = 1_000_</script>` // Faulty JS
	req := httptest.NewRequest(http.MethodGet, "/", nil)
	rec := httptest.NewRecorder()
	m.Middleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/html")
		_, _ = w.Write([]byte(input))

		if err = w.(io.Closer).Close(); err != nil {
			panic(err)
		}
	})).ServeHTTP(rec, req)
}
ResponseWriter
func Serve(w http.ResponseWriter, r *http.Request) {
	mw := m.ResponseWriter(w, r)
	defer mw.Close()
	w = mw

	http.ServeFile(w, r, path.Join("www", r.URL.Path))
}
Custom response writer

ResponseWriter example which returns a ResponseWriter that minifies the content and then writes to the original ResponseWriter. Any write after applying this filter will be minified.

type MinifyResponseWriter struct {
	http.ResponseWriter
	io.WriteCloser
}

func (m MinifyResponseWriter) Write(b []byte) (int, error) {
	return m.WriteCloser.Write(b)
}

// MinifyResponseWriter must be closed explicitly by calling site.
func MinifyFilter(mediatype string, res http.ResponseWriter) MinifyResponseWriter {
	m := minify.New()
	// add minfiers

	mw := m.Writer(mediatype, res)
	return MinifyResponseWriter{res, mw}
}

// Usage
func(w http.ResponseWriter, req *http.Request) {
	w = MinifyFilter("text/html", w)
	if _, err := io.WriteString(w, "<p class="message"> This HTTP response will be minified. </p>"); err != nil {
		panic(err)
	}
	if err := w.Close(); err != nil {
		panic(err)
	}
	// Output: <p class=message>This HTTP response will be minified.
}
Templates

Here's an example of a replacement for template.ParseFiles from template/html, which automatically minifies each template before parsing it.

Be aware that minifying templates will work in most cases but not all. Because the HTML minifier only works for valid HTML5, your template must be valid HTML5 of itself. Template tags are parsed as regular text by the minifier.

func compileTemplates(filenames ...string) (*template.Template, error) {
	m := minify.New()
	m.AddFunc("text/html", html.Minify)

	var tmpl *template.Template
	for _, filename := range filenames {
		name := filepath.Base(filename)
		if tmpl == nil {
			tmpl = template.New(name)
		} else {
			tmpl = tmpl.New(name)
		}

		b, err := os.ReadFile(filename)
		if err != nil {
			return nil, err
		}

		mb, err := m.Bytes("text/html", b)
		if err != nil {
			return nil, err
		}
		tmpl.Parse(string(mb))
	}
	return tmpl, nil
}

Example usage:

templates := template.Must(compileTemplates("view.html", "home.html"))

FAQ

Newlines remain in minified output

While you might expect the minified output to be on a single line for it to be fully minified, this is not true. In many cases, using a literal newline doesn't affect the file size, and in some cases it may even reduce the file size.

A typical example is HTML. Whitespace is significant in HTML, meaning that spaces and newlines between or around tags may affect how they are displayed. There is no distinction between a space or a newline and they may be interchanged without affecting the displayed HTML. Remember that a space (0x20) and a newline (0x0A) are both one byte long, so that there is no difference in file size when interchanging them. This minifier removes unnecessary whitespace by replacing stretches of spaces and newlines by a single whitespace character. Specifically, if the stretch of white space characters contains a newline, it will replace it by a newline and otherwise by a space. This doesn't affect the file size, but may help somewhat for debugging or file transmission objectives.

Another example is JavaScript. Single or double quoted string literals may not contain newline characters but instead need to escape them as \n. These are two bytes instead of a single newline byte. Using template literals it is allowed to have literal newline characters and we can use that fact to shave-off one byte! The result is that the minified output contains newlines instead of escaped newline characters, which makes the final file size smaller. Of course, changing from single or double quotes to template literals depends on other factors as well, and this minifier makes a calculation whether the template literal results in a shorter file size or not before converting a string literal.

License

Released under the MIT license.

Documentation

Overview

Package minify relates MIME type to minifiers. Several minifiers are provided in the subpackages.

Index

Examples

Constants

View Source 
const MaxInt = int(^uint(0) >> 1)

MaxInt is the maximum value of int.

View Source 
const MinInt = -MaxInt - 1

MinInt is the minimum value of int.

Variables

View Source 
var Epsilon = 0.00001

Epsilon is the closest number to zero that is not considered to be zero.

View Source 
var ErrClosedWriter = errors.New("write on closed writer") // TODO: DEPRECATED, remove

ErrClosedWriter is returned when writing to a closed writer.

View Source 
var ErrNotExist = errors.New("minifier does not exist for mimetype")

ErrNotExist is returned when no minifier exists for a given mimetype.

View Source 
var Warning = log.New(os.Stderr, "WARNING: ", 0)

Warning is used to report usage warnings such as using a deprecated feature

Functions

func DataURI 

func DataURI(m *M, dataURI []byte) []byte

DataURI minifies a data URI and calls a minifier by the specified mediatype. Specifications: https://www.ietf.org/rfc/rfc2397.txt.

func Decimal 

func Decimal(num []byte, prec int) []byte

Decimal minifies a given byte slice containing a decimal and removes superfluous characters. It differs from Number in that it does not parse exponents. It does not parse or output exponents. prec is the number of significant digits. When prec is zero it will keep all digits. Only digits after the dot can be removed to reach the number of significant digits. Very large number may thus have more significant digits.

func Mediatype 

func Mediatype(b []byte) []byte

Mediatype minifies a given mediatype by removing all whitespace and lowercasing all parts except strings (which may be case sensitive).

func Number 

func Number(num []byte, prec int) []byte

Number minifies a given byte slice containing a number and removes superfluous characters.

func UpdateErrorPosition added in v2.9.16 

func UpdateErrorPosition(err error, input *parse.Input, offset int) error

Types

type M 

type M struct {
	URL *url.URL
	// contains filtered or unexported fields
}

M holds a map of mimetype => function to allow recursive minifier calls of the minifier functions.

func New 

func New() *M

New returns a new M.

func (*M) Add 

func (m *M) Add(mimetype string, minifier Minifier)

Add adds a minifier to the mimetype => function map (unsafe for concurrent use).

func (*M) AddCmd 

func (m *M) AddCmd(mimetype string, cmd *exec.Cmd)

AddCmd adds a minify function to the mimetype => function map (unsafe for concurrent use) that executes a command to process the minification. It allows the use of external tools like ClosureCompiler, UglifyCSS, etc. for a specific mimetype.

func (*M) AddCmdRegexp 

func (m *M) AddCmdRegexp(pattern *regexp.Regexp, cmd *exec.Cmd)

AddCmdRegexp adds a minify function to the mimetype => function map (unsafe for concurrent use) that executes a command to process the minification. It allows the use of external tools like ClosureCompiler, UglifyCSS, etc. for a specific mimetype regular expression.

func (*M) AddFunc 

func (m *M) AddFunc(mimetype string, minifier MinifierFunc)

AddFunc adds a minify function to the mimetype => function map (unsafe for concurrent use).

func (*M) AddFuncRegexp 

func (m *M) AddFuncRegexp(pattern *regexp.Regexp, minifier MinifierFunc)

AddFuncRegexp adds a minify function to the mimetype => function map (unsafe for concurrent use).

func (*M) AddRegexp 

func (m *M) AddRegexp(pattern *regexp.Regexp, minifier Minifier)

AddRegexp adds a minifier to the mimetype => function map (unsafe for concurrent use).

func (*M) Bytes 

func (m *M) Bytes(mediatype string, v []byte) ([]byte, error)

Bytes minifies an array of bytes (safe for concurrent use). When an error occurs it return the original array and the error. It returns an error when no such mimetype exists (ErrNotExist) or any error occurred in the minifier function.

func (*M) Match 

func (m *M) Match(mediatype string) (string, map[string]string, MinifierFunc)

Match returns the pattern and minifier that gets matched with the mediatype. It returns nil when no matching minifier exists. It has the same matching algorithm as Minify.

func (*M) Middleware 

func (m *M) Middleware(next http.Handler) http.Handler

Middleware provides a middleware function that minifies content on the fly by intercepting writes to http.ResponseWriter. http.ResponseWriter loses all functionality such as Pusher, Hijacker, Flusher, ... Minification might be slower than just sending the original file! Caching is advised.

func (*M) MiddlewareWithError added in v2.11.0 

func (m *M) MiddlewareWithError(next http.Handler, errorFunc func(w http.ResponseWriter, r *http.Request, err error)) http.Handler

MiddlewareWithError provides a middleware function that minifies content on the fly by intercepting writes to http.ResponseWriter. The error function allows handling minification errors. http.ResponseWriter loses all functionality such as Pusher, Hijacker, Flusher, ... Minification might be slower than just sending the original file! Caching is advised.

func (*M) Minify 

func (m *M) Minify(mediatype string, w io.Writer, r io.Reader) error

Minify minifies the content of a Reader and writes it to a Writer (safe for concurrent use). An error is returned when no such mimetype exists (ErrNotExist) or when an error occurred in the minifier function. Mediatype may take the form of 'text/plain', 'text/*', '*/*' or 'text/plain; charset=UTF-8; version=2.0'.

Example (Custom) 
m := New()
m.AddFunc("text/plain", func(m *M, w io.Writer, r io.Reader, _ map[string]string) error {
	// remove all newlines and spaces
	rb := bufio.NewReader(r)
	for {
		line, err := rb.ReadString('\n')
		if err != nil && err != io.EOF {
			return err
		}
		if _, errws := io.WriteString(w, strings.ReplaceAll(line, " ", "")); errws != nil {
			return errws
		}
		if err == io.EOF {
			break
		}
	}
	return nil
})

in := "Because my coffee was too cold, I heated it in the microwave."
out, err := m.String("text/plain", in)
if err != nil {
	panic(err)
}
fmt.Println(out)

Output:

Becausemycoffeewastoocold,Iheateditinthemicrowave.

func (*M) MinifyMimetype 

func (m *M) MinifyMimetype(mimetype []byte, w io.Writer, r io.Reader, params map[string]string) error

MinifyMimetype minifies the content of a Reader and writes it to a Writer (safe for concurrent use). It is a lower level version of Minify and requires the mediatype to be split up into mimetype and parameters. It is mostly used internally by minifiers because it is faster (no need to convert a byte-slice to string and vice versa).

func (*M) Reader 

func (m *M) Reader(mediatype string, r io.Reader) io.Reader

Reader wraps a Reader interface and minifies the stream. Errors from the minifier are returned by the reader.

Example 
b := bytes.NewReader([]byte("input"))

m := New()
// add minfiers

r := m.Reader("mime/type", b)
if _, err := io.Copy(os.Stdout, r); err != nil {
	if _, err := io.Copy(os.Stdout, b); err != nil {
		panic(err)
	}
}

Output:

func (*M) ResponseWriter 

func (m *M) ResponseWriter(w http.ResponseWriter, r *http.Request) *responseWriter

ResponseWriter minifies any writes to the http.ResponseWriter. http.ResponseWriter loses all functionality such as Pusher, Hijacker, Flusher, ... Minification might be slower than just sending the original file! Caching is advised.

func (*M) String 

func (m *M) String(mediatype string, v string) (string, error)

String minifies a string (safe for concurrent use). When an error occurs it return the original string and the error. It returns an error when no such mimetype exists (ErrNotExist) or any error occurred in the minifier function.

func (*M) Writer 

func (m *M) Writer(mediatype string, w io.Writer) io.WriteCloser

Writer wraps a Writer interface and minifies the stream. Errors from the minifier are returned by Close on the writer. The writer must be closed explicitly.

Example 
m := New()
// add minfiers

w := m.Writer("mime/type", os.Stdout)
if _, err := w.Write([]byte("input")); err != nil {
	panic(err)
}
if err := w.Close(); err != nil {
	panic(err)
}

Output:

type Minifier 

type Minifier interface {
	Minify(*M, io.Writer, io.Reader, map[string]string) error
}

Minifier is the interface for minifiers. The *M parameter is used for minifying embedded resources, such as JS within HTML.

type MinifierFunc 

type MinifierFunc func(*M, io.Writer, io.Reader, map[string]string) error

MinifierFunc is a function that implements Minifer.

func (MinifierFunc) Minify 

func (f MinifierFunc) Minify(m *M, w io.Writer, r io.Reader, params map[string]string) error

Minify calls f(m, w, r, params)

Source Files

View all Source files

Directories

Path Synopsis
bindings
js
py
cmd
minify
Package css minifies CSS3 following the specifications at http://www.w3.org/TR/css-syntax-3/.
 Package css minifies CSS3 following the specifications at http://www.w3.org/TR/css-syntax-3/.
Package html minifies HTML5 following the specifications at http://www.w3.org/TR/html5/syntax.html.
 Package html minifies HTML5 following the specifications at http://www.w3.org/TR/html5/syntax.html.
Package js minifies ECMAScript 2021 following the language specification at https://tc39.es/ecma262/.
 Package js minifies ECMAScript 2021 following the language specification at https://tc39.es/ecma262/.
Package json minifies JSON following the specifications at http://json.org/.
 Package json minifies JSON following the specifications at http://json.org/.
Package svg minifies SVG1.1 following the specifications at http://www.w3.org/TR/SVG11/.
 Package svg minifies SVG1.1 following the specifications at http://www.w3.org/TR/SVG11/.
Package xml minifies XML1.0 following the specifications at http://www.w3.org/TR/xml/.
 Package xml minifies XML1.0 following the specifications at http://www.w3.org/TR/xml/.

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