PostCSS Preset Env
PostCSS Preset Env lets you convert modern CSS into something most browsers
can understand, determining the polyfills you need based on your targeted
browsers or runtime environments.
npm install postcss-preset-env
@custom-media --viewport-medium (width <= 50rem);
@custom-selector :--heading h1, h2, h3, h4, h5, h6;
:root {
--mainColor: #12345678;
}
body {
color: var(--mainColor);
font-family: system-ui;
overflow-wrap: break-word;
}
:--heading {
background-image: image-set(url(img/heading.png) 1x, url(img/heading@2x.png) 2x);
@media (--viewport-medium) {
margin-block: 0;
}
}
a {
color: rebeccapurple;
&:hover {
color: color-mod(var(--mainColor) alpha(80%));
}
}
/* becomes */
:root {
--mainColor: rgba(18, 52, 86, 0.47059);
}
body {
color: rgba(18, 52, 86, 0.47059);
color: var(--mainColor);
font-family: system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen, Ubuntu, Cantarell, Droid Sans, Helvetica Neue;
word-wrap: break-word;
}
h1, h2, h3, h4, h5, h6 {
background-image: url(img/heading.png);
}
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
h1, h2, h3, h4, h5, h6 {
background-image: url(img/heading@2x.png)
}
}
@media (max-width: 50rem) {
h1, h2, h3, h4, h5, h6 {
margin-top: 0;
margin-bottom: 0;
}
}
a {
color: #639
}
a:hover {
color: rgba(18, 52, 86, 0.8);
}
Without any configuration options, PostCSS Preset Env enables Stage 2
features and supports all browsers.
Usage
Add PostCSS Preset Env to your project:
npm install postcss-preset-env --save-dev
Node
Use PostCSS Preset Env to process your CSS:
import postcssPresetEnv from 'postcss-preset-env';
postcssPresetEnv.process(YOUR_CSS);
PostCSS
Add PostCSS to your project:
npm install postcss --save-dev
Use PostCSS Preset Env as a plugin:
import postcss from 'gulp-postcss';
import postcssPresetEnv from 'postcss-preset-env';
postcss([
postcssPresetEnv()
]).process(YOUR_CSS);
Webpack
Add PostCSS Loader to your project:
npm install postcss-loader --save-dev
Use PostCSS Preset Env in your Webpack configuration:
import postcssPresetEnv from 'postcss-preset-env';
export default {
module: {
rules: [
{
test: /\.css$/,
use: [
'style-loader',
{ loader: 'css-loader', options: { importLoaders: 1 } },
{ loader: 'postcss-loader', options: {
ident: 'postcss',
plugins: () => [
postcssPresetEnv()
]
} }
]
}
]
}
};
Create React App
Add React App Rewired and React App Rewire PostCSS to your project:
npm install react-app-rewired react-app-rewire-postcss --save-dev
Use React App Rewire PostCSS and PostCSS Preset Env in your
config-overrides.js
file:
import reactAppRewirePostcss from 'react-app-rewire-postcss';
import postcssPresetEnv from 'postcss-preset-env';
export default config => reactAppRewirePostcss(config, {
plugins: () => [
postcssPresetEnv()
]
});
Gulp
Add Gulp PostCSS to your build tool:
npm install gulp-postcss --save-dev
Use PostCSS Preset Env in your Gulpfile:
import postcss from 'gulp-postcss';
import postcssPresetEnv from 'postcss-preset-env';
gulp.task('css', () => gulp.src('./src/*.css').pipe(
postcss([
postcssPresetEnv()
])
).pipe(
gulp.dest('.')
));
Grunt
Add Grunt PostCSS to your project:
npm install grunt-postcss --save-dev
Use PostCSS Preset Env in your Gruntfile:
import postcssPresetEnv from 'postcss-preset-env';
grunt.loadNpmTasks('grunt-postcss');
grunt.initConfig({
postcss: {
options: {
use: [
postcssPresetEnv()
]
},
dist: {
src: '*.css'
}
}
});
Options
stage
The stage
option determines which CSS features to polyfill, based upon their
stability in the process of becoming implemented web standards. The stages are
0 through 4.
postcssPresetEnv({
stage: 0
})
Setting the stage
option to false
will disable all of the polyfills. Doing
this would only be useful if you intended to exclusively use the
features
option.
Without any configuration options, PostCSS Preset Env enables Stage 2
features.
features
The features
option enables or disables specific polyfills. Passing true
to
a specific feature id will enable its polyfill, while passing false
will
disable it.
postcssPresetEnv({
stage: 3,
features: {
'nesting-rules': true
}
})
Passing an object {}
to a specific feature id will enable and
configure it.
postcssPresetEnv({
stage: 3,
features: {
'color-mod-function': {
unresolved: 'warn'
}
}
})
Any polyfills not explicitly enabled or disabled through features
are
determined by the stage
option.
browsers
The browsers
option determines which browsers are being supported, which is
used to further enable or disable polyfills, based upon their support matrix
found at caniuse.
PostCSS Preset Env supports any standard browserslist configuration, which
includes a .browserslistrc
file, a browserslist
key in package.json
, or
browserslist
environment variables.
The browsers
option should only be used when a standard browserslist
configuration is not available.
postcssPresetEnv({
browsers: 'last 2 versions'
})
If not valid browserslist configuration is specified, the
default browserslist query
will be used.
insertBefore / insertAfter
The insertBefore
and insertAfter
keys allow you to insert other PostCSS
plugins into the chain. This is only useful if you are also using sugary
PostCSS plugins that must execute before or after certain polyfills.
Both insertBefore
and insertAfter
support chaining one or multiple plugins.
import postcssSimpleVars from 'postcss-simple-vars';
postcssPresetEnv({
insertBefore: {
'all-property': postcssSimpleVars
}
})
autoprefixer
The autoprefixer
option passes
additional options
into autoprefixer.