postcss-plugin-px2em

Features

A plugin for PostCSS that generates em units from pixel units.

Installation

$ npm i --save postcss-plugin-px2em

Usage

input and output

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

// output
h1 {
  margin: 0 0 0.2em;
  font-size: 0.32em;
  line-height: 1.2;
  letter-spacing: 0.01em;
}

original

import { writeFile, readFileSync } from 'fs';
import postcss from 'postcss';
import pxtorem from 'postcss-plugin-px2em';

const css = readFileSync('/path/to/test.css', 'utf8');
const options = {
  replace: false,
};
const processedCss = postcss(pxtorem(options)).process(css).css;

writeFile('/path/to/test.rem.css', processedCss, err => {
  if (err) throw err;
  console.log('Rem file written.');
});

with webpack

import px2em from 'postcss-plugin-px2em';
const px2emOpts = {
  ......
};
 
export default {
  module: {
    loaders: [
      {
        test: /\.css$/,
        loader: 'style-loader!css-loader!postcss-loader',
      },
    ],
  },
  postcss: [px2em(px2emOpts)],
}

with atool-build

webpack.connfig.js

import webpack from 'atool-build/lib/webpack';
import px2em from 'postcss-plugin-px2em';

export default webpackConfig => {
  const px2emOpts = {
    ......
  };
  webpackConfig.postcss.push(px2em(px2emOpts));

  return webpackConfig;
};

Configuration

Default:

{
  rootValue: 100,
  unitPrecision: 5,
  propWhiteList: [],
  propBlackList: [],
  exclude:false,
  selectorBlackList: [],
  ignoreIdentifier: false,
  replace: true,
  mediaQuery: false,
  minPixelValue: 0
}

• rootValue (Number|Object) The root element font size. Default is 100.
  • If rootValue is an object, for example { px: 50, rpx: 100 }, it will replace rpx to 1/100 rem , and px to 1/50 rem.
• unitPrecision (Number) The decimal numbers to allow the REM units to grow to.
• propWhiteList (Array) The properties that can change from px to rem.
  • Default is an empty array that means disable the white list and enable all properties.
  • Values need to be exact matches.
• propBlackList (Array) The properties that should not change from px to rem.
  • Values need to be exact matches.
• exclude (Reg) a way to exclude some folder,eg. /(node_module)/.
• selectorBlackList (Array) The selectors to ignore and leave as px.
  • 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
• ignoreIdentifier (Boolean/String) a way to have a single property ignored, when ignoreIdentifier enabled, then replace would be set to true automatically.
• 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.

License

MIT