postcss-rem-to-pixel-next 

A plugin for PostCSS that generates px units from rem units.

Acknowledgements

This project is an updated version of the original postcss-rem-to-pixel plugin, which was created by jesstech. All credit for the original concept and implementation goes to them.

I have updated the plugin to utilize the new PostCSS 8 API.

Install

``shell
$ npm i postcss-rem-to-pixel-next --save-dev
`

Usage

Sometimes you need to include a third-party css file that uses rems. Great pracitice! Unless you can't afford to change your body font-size just for some vendor. This script converts every rem value to a px value from the properties you choose using a default font size of 16px.

$3

_With the default settings, only font related properties are targeted._

`css
// input
h1 {
margin: 0 0 20px;
font-size: 2rem;
line-height: 1.2;
letter-spacing: 0.0625rem;
}

// output
h1 {
margin: 0 0 20px;
font-size: 32px;
line-height: 1.2;
letter-spacing: 1px;
}
`

$3

`js
var fs = require("fs");
var postcss = require("postcss");
var remToPx = require("postcss-rem-to-pixel");
var css = fs.readFileSync("main.css", "utf8");
var options = {
replace: false,
};
var processedCss = postcss(remToPx(options)).process(css).css;

fs.writeFile("main-px.css", processedCss, function (err) {
if (err) {
throw err;
}
console.log("Rem file written.");
});
`

$3

Type: Object | Null
Default:

`js
{
rootValue: 16,
unitPrecision: 5,
propList: ['font', 'font-size', 'line-height', 'letter-spacing'],
selectorBlackList: [],
replace: true,
mediaQuery: false,
minRemValue: 0
}
`

- rootValue (Number) The root element font size.
- unitPrecision (Number) The decimal precision px units are allowed to use, floored (rounding down on half).
- propList (Array) The properties that can change from rem to px.
- Values need to be exact matches.
- Use wildcard to enable all properties. Example: ['']
- Use at the start or end of a word. (['position*'] will match background-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 rem.
- 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 match body but not .body
- replace (Boolean) replaces rules containing rems instead of adding fallbacks.
- mediaQuery (Boolean) Allow rem to be converted in media queries.
- minRemValue (Number) Set the minimum rem value to replace.

$3

`js
var gulp = require("gulp");
var postcss = require("gulp-postcss");
var autoprefixer = require("autoprefixer");
var remToPx = require("postcss-rem-to-pixel");

gulp.task("css", function () {
var processors = [
autoprefixer({
browsers: "last 1 version",
}),
remToPx({
replace: false,
}),
];

return gulp
.src(["build/css/*/.css"])
.pipe(postcss(processors))
.pipe(gulp.dest("build/css"));
});
`

$3

Currently, the easiest way to have a single property ignored is to use a capital in the rem unit declaration.

`css
// rem is converted to px
.convert {
font-size: 1rem; // converted to 16px
}

// Rem or REM is ignored by postcss-rem-to-pixel but still accepted by browsers
.ignore {
border: 1Rem solid; // ignored
border-width: 2REM; // ignored
}
``