postcss-vw2rem
v1.0.1
Published
A CSS post-processor that converts vw to rem.
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postcss-vw2rem
A plugin for PostCSS that generates rem units from vw units.
This project is forked from postcss-pxtorem under the MIT license.
Why
In some tablet or android fold devices, someone may think that arbitrarily scalling the size is inappropriate and that the size needs to be limited. vw
is directly related to screen width, while rem
can be restricted.
Install
$ npm install postcss postcss-vw2rem --save-dev
Usage
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 vw value to a rem from the properties you choose to allow the browser to set the font size.
Note
rootValue
below is set to 16
, so you can relate to the examples of postcss-pxtorem
.
While the default value is set to 10
in real project⚠️.
Input/Output
With the default settings, only font related properties are targeted.
// input
h1 {
margin: 0 0 20vw;
font-size: 32vw;
line-height: 1.2;
letter-spacing: 1vw;
}
// output
h1 {
margin: 0 0 20vw;
font-size: 2rem;
line-height: 1.2;
letter-spacing: 0.0625rem;
}
Example
var fs = require('fs');
var postcss = require('postcss');
var vw2rem = require('postcss-vw2rem');
var css = fs.readFileSync('main.css', 'utf8');
var options = {
replace: false
};
var processedCss = postcss(vw2rem(options)).process(css).css;
fs.writeFile('main-rem.css', processedCss, function (err) {
if (err) {
throw err;
}
console.log('Rem file written.');
});
options
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 theinput
parameterunitPrecision
(Number) The decimal numbers to allow the REM units to grow to.propList
(Array) The properties that can change from vw to rem.- Values need to be exact matches.
- Use wildcard
*
to enable all properties. Example:['*']
- Use
*
at the start or end of a word. (['*position*']
will matchbackground-position-y
) - Use
!
to not match a property. Example:['*', '!letter-spacing']
- Combine the "not" prefix with the other prefixes. Example:
['*', '!font*']
selectorBlackList
(Array) The selectors to ignore and leave as vw.- If value is string, it checks to see if selector contains the string.
['body']
will match.body-class
- If value is regexp, it checks to see if the selector matches the regexp.
[/^body$/]
will matchbody
but not.body
- If value is string, it checks to see if selector contains the string.
replace
(Boolean) Replaces rules containing rems instead of adding fallbacks.mediaQuery
(Boolean) Allow vw 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 vw.- If value is string, it checks to see if file path contains the string.
'exclude'
will match\project\postcss-vw2rem\exclude\path
- If value is regexp, it checks to see if file path matches the regexp.
/exclude/i
will match\project\postcss-vw2rem\exclude\path
- If value is function, you can use exclude function to return a true and the file will be ignored.
- the callback will pass the file path as a parameter, it should returns a Boolean result.
function (file) { return file.indexOf('exclude') !== -1; }
- If value is string, it checks to see if file path contains the string.
unit
(String) Set the default unit to convert, default isvw
.
Use with gulp-postcss and autoprefixer
var gulp = require('gulp');
var postcss = require('gulp-postcss');
var autoprefixer = require('autoprefixer');
var vw2rem = require('postcss-vw2rem');
gulp.task('css', function () {
var processors = [
autoprefixer({
browsers: 'last 1 version'
}),
vw2rem({
replace: false
})
];
return gulp.src(['build/css/**/*.css'])
.pipe(postcss(processors))
.pipe(gulp.dest('build/css'));
});
A message about ignoring properties
Currently, the easiest way to have a single property ignored is to use a capital in the pixel unit declaration.
// `vw` is converted to `rem`
.convert {
font-size: 16vw; // converted to 1rem
}
// `Vx` or `VW` is ignored by `postcss-vw2rem` but still accepted by browsers
.ignore {
border: 1vw solid; // ignored
border-width: 2vw; // ignored
}