cuth / postcss-data-packer

PostCSS plugin to move an embedded data to separate file

postcss-data-packer

PostCSS plugin to move an embedded data into a separate file. It can also combine selectors of rules with the same data!

Embedded data can be used in value of these properties: background, background-image, border-image, src (@font-face), content (pseudoelements).

Regexp /url\(["']?data/g is using to detect a data in values.

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Installation

npm install postcss-data-packer

How to use

Options

dataFile (default: true)

Plugin can work in two modes: dataFile: false removes all embedded data from stylesheet, dataFile: true removes everything except data.

pure (default: true)

Plugin can combine selectors of rules with the same data to minimize output.

Selectors are combined in first rule with a corresponding pair property-value of declaration.

.a { background-image: url(/*a.png*/); }
.b { background-image: url(/*a.png*/); }
.c { background-image: url(/*a.png*/); }

.a,
.b,
.c { background-image: url(/*a.png*/); }

This feature could lead to problems:

.a { background-image: url(/*a.png*/) }
.b { background-image: url(/*b.png*/) }
.c { background-image: url(/*a.png*/) }

.a,
.c { background-image: url(/*a.png*/) }
.b { background-image: url(/*b.png*/) }

An element <div class="b c"></div> will use only styles of .b because specifity of .c is lower, although .c is declared later in main file.

Note that a reliable gzip can replace this function because duplicate rows can be easily compressed.

dest (default: false)

You can generate data file directly by plugin.

Define by dest.path path of saving data file.

dest.map (default: false) is for set up source map creation of data file. You can set it up like in PostCSS manual.

If you do not want inline source map, you can set path for it by annotation. This path is relative to data file.

In next case you will get two files: /css/main_data.css and /css/maps/main_data.css.map.

dataPacker({
	dest: {
		path: 'css/main_data.css',
		map: {
			inline: false,
			annotation: 'maps/main_data.css.map'
		}
	}
})

If you do not need source map, you can set path for saving just like this:

dataPacker({
	dest: 'css/main_data.css'
})

Using

Plugin can be used just like any other PostCSS plugin. For example, Gulp setup (using gulp-postcss):

var gulp = require('gulp');
var rename = require('gulp-rename');

var postcss = require('gulp-postcss');

gulp.task('processcss', function () {
	var processors = [
		require('postcss-data-packer')({
			dest: 'css/main_data.css'
		})
	];
	gulp.src('css/main.css')
		.pipe(postcss(processors))
		.pipe(gulp.dest('css'));
});

gulp.task('default', function () {
	gulp.watch('css/main.css', ['processcss']);
});

And Grunt setup (using grunt-postcss):

module.exports = function(grunt) {
	require('load-grunt-tasks')(grunt);

	grunt.initConfig({
		postcss: {
			files: {
				options: {
					map: false,
					processors: [
						require('postcss-data-packer')({
							dest: 'css/main_data.css'
						})
					]
				},
				src: 'css/main.css'
			}
		}
	});

	return grunt.registerTask('default', ['postcss']);
};

(see other usage options in docs of PostCSS)

And then declare these files in the markup:

<!-- Data is before main styles to simplify the redefinition of declarations -->
<link rel="stylesheet" href="main_data.css">
<link rel="stylesheet" href="main.css">