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postcss-unit-transformer
Advanced tools
A plugin for PostCSS that generates rem units from pixel units.
$ npm install postcss postcss-unit-transformer --save-dev
Pixels are the easiest unit to use (opinion). The only issue with them is that they don't let browsers change the default font size of 16. This script converts every px value to a rem from the properties you choose to allow the browser to set the font size.
With the default settings, only font related properties are targeted.
// input
h1 {
margin: 0 0 20px;
font-size: 32px;
line-height: 1.2;
letter-spacing: 1px;
}
// output
h1 {
margin: 0 0 20px;
font-size: 2rem;
line-height: 1.2;
letter-spacing: 0.0625rem;
}
var fs = require('fs');
var postcss = require('postcss');
var unitTransformer = require('postcss-unit-transformer');
var css = fs.readFileSync('main.css', 'utf8');
var options = {
replace: false
};
var processedCss = postcss(unitTransformer(options)).process(css).css;
fs.writeFile('main-rem.css', processedCss, function (err) {
if (err) {
throw err;
}
console.log('Rem file written.');
});
Type: Object | Null
Default:
{
rootValue: 16,
unitPrecision: 5,
propList: ['font', 'font-size', 'line-height', 'letter-spacing', 'word-spacing'],
selectorBlackList: [],
replace: true,
mediaQuery: false,
minPixelValue: 0,
exclude: /node_modules/i
}
rootValue
(Number | Function) Represents the root element font size or returns the root element font size based on the input
parameterunitPrecision
(Number) The decimal numbers to allow the REM units to grow to.propList
(Array) The properties that can change from px to rem.
*
to enable all properties. Example: ['*']
*
at the start or end of a word. (['*position*']
will match background-position-y
)!
to not match a property. Example: ['*', '!letter-spacing']
['*', '!font*']
selectorBlackList
(Array) The selectors to ignore and leave as px.
['body']
will match .body-class
[/^body$/]
will match body
but not .body
replace
(Boolean) Replaces rules containing rems instead of adding fallbacks.mediaQuery
(Boolean) Allow px to be converted in media queries.minPixelValue
(Number) Set the minimum pixel value to replace.exclude
(String, Regexp, Function) The file path to ignore and leave as px.
'exclude'
will match \project\postcss-unit-transformer\exclude\path
/exclude/i
will match \project\postcss-unit-transformer\exclude\path
function (file) { return file.indexOf('exclude') !== -1; }
unit
(String) Set the default unit to convert, default is px
.var gulp = require('gulp');
var postcss = require('gulp-postcss');
var autoprefixer = require('autoprefixer');
var unitTransformer = require('postcss-unit-transformer');
gulp.task('css', function () {
var processors = [
autoprefixer({
browsers: 'last 1 version'
}),
unitTransformer({
replace: false
})
];
return gulp.src(['build/css/**/*.css'])
.pipe(postcss(processors))
.pipe(gulp.dest('build/css'));
});
Currently, the easiest way to have a single property ignored is to use a capital in the pixel unit declaration.
// `px` is converted to `rem`
.convert {
font-size: 16px; // converted to 1rem
}
// `Px` or `PX` is ignored by `postcss-unit-transformer` but still accepted by browsers
.ignore {
border: 1Px solid; // ignored
border-width: 2PX; // ignored
}
FAQs
A CSS post-processor that converts px to rem or other.
We found that postcss-unit-transformer demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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