modernizr-auto-loader for webpack

This loader uses Modernizr/customizr to "...crawl your project for Modernizr test references and save out a minified, uglified, customized version using only the tests you've used in your JavaScript or (S)CSS.".

It outputs a self executing module, which automatically loads your custom modernizr build, and it also updates on all webpack rebuilds. Yay! Automagic!

Installation

$ npm install --save-dev modernizr-auto-loader

Usage

.modernizr-autorc configuration file

Documentation: Using loaders

Create a .modernizr-autorc configuration file (in valid JSON format), preferably in your project root, and put your customizr config details in it. , like this:

// .modernizr-autorc
{
  "option": "value"
}

The default configuration used by this loader, which will be extended by your custom config is:

// default config
{
	"options": ["setClasses", "addTest", "html5printshiv", "testProp", "fnBind"],
	"files": {
		"src": ["**[^node_modules]/**/*.{js,css,scss}"]
	}
}

(See the Customizr documentation for all available options.)

As specified in the default config, modernizr-auto-loader crawls all js/css/scss files except files in node_modules (pattern **[^node_modules]/**/*.{js,css,scss}) by default, so it's recommended to specify your own file patterns to speed things up, or in worst case, have customizr abort due to too many open files.

The following config makes customizer only traverse an assets folder, looking for js/jsx/css/scss files.

// .modernizr-autorc
{
  "files": {
    "src": [
      "assets/**/*.{js,jsx,css,scss}"
    ]
  }
}

If you want modernizr-auto-loader to only run once on startup of the webpack build, you can by adding runOnce: true to the configuration file, like this:

// .modernizr-autorc
{
  "files": {
    "src": [
      "assets/**/*.{js,jsx,css,scss}"
    ]
  },
  "runOnce": true
}

webpack configuration

Adjust your webpack config to trigger modernizr-auto-loader on build. If you didn't put your config in the root folder, resolve the path relative to your webpack config.

module.exports = {
  module: {
    loaders: [
      {
        test: /\.modernizr-autorc$/,
        loader: "modernizr-auto-loader"
      }
    ]
  },
  resolve: {
    alias: {
      modernizr$: path.resolve(__dirname, ".modernizr-autorc")
    }
  }
}

JS integration

Finally, require the configuration file (with a full relative path) somewhere in your source file (typically your entry point) or even simpler, just require 'modernizr'.

// require config file with relative path (makes ESLint module/file resolvers happy)
require("relative/path/to/.modernizr-autorc");

// OR, require modernizr
require("modernizr"); // es5

Since Modernizr is a global, you can also test for features in your JS files, like this:

if (!Modernizr.promises) {
    // ...
}

If you're using ESLint, make sure Modernizr is added as a global to prevent no-undef errors.

Inspired by

This loader is inspired by gulp-modernizr and modernizr-loader.