CSS custom properties polyfill for ie11

Question

Is there a way to pollyfill a custom CSS property for ie11 with JavaScript? I was thinking on load, check if browser supports custom properties and if not do some kind of find a

Answer 1

You didn't mention how you're bundling your JavaScript, but yes, it's possible. For example, PostCSS has a plugin, which polyfills this feature.

The usage depends on how you're bundling your script files. With Webpack, for example, you'd define this plugin in your postcss config or import it as a plugin under your webpack config:

// webpack.config.js:
module.exports = {
  module: {
    rules: [
        {
            test: /\.css$/,
            use: ["style-loader", "css-loader", "postcss-loader"]
        }
    ]
  }
}

// postcss.config.js
module.exports = {
  plugins: [
    require('postcss-custom-properties'),
    require('autoprefixer'),
    // any other PostCSS plugins
  ]
}

The plugin also has an example for programmatic usage (as a separate node script):

// dependencies
var fs = require('fs')
var postcss = require('postcss')
var customProperties = require('postcss-custom-properties')

// css to be processed
var css = fs.readFileSync('input.css', 'utf8')

// process css using postcss-custom-properties
var output = postcss()
  .use(customProperties())
  .process(css)
  .css