@iodigital/criticalcss

This node module makes it possible to generate critical css bundles from different pages in different viewports. It uses GitHub - addyosmani/critical under the hood.

Usage

Install

npm install @iodigital/criticalcss

Configuration

First add a configuration file in the root of your project, named criticalcss.config.js. This file should contain a const config for generating critical css and a const pages with the urls and dimensions for the viewport. Example configuration:

const config = {
    rebase: (asset) => { // absolute assets path
        if (asset.pathname !== null && asset.pathname === asset.originUrl) {
            return asset.absolutePath;
        }
        return asset.url;
    },
    dimensions: [
        {"width": 320}, // height is optional
        {"width": 767, "height": 3000},
        {"width": 992},
        {"width": 1200},
        {"width": 1424}
    ],
    penthouse: {
        timeout: 60000,
        forceExclude: [
            ".footer__columns--wrapper>.footer__column:nth-of-type(4) img"
        ]
    }
}

const pages = {
    "domain": "https://site.com",
    "pages": [
        {
            "src": "/",
            "target": "app/design/frontend/THEMEPATH/THEMEPATH/web/css/cms-critical.css"
        },
        {
            "src": "/category/",
            "target": "app/design/frontend/THEMEPATH/THEMEPATH/web/css/category-critical.css"
        },
        {
            "src": "/some-product.html",
            "target": "app/design/frontend/THEMEPATH/THEMEPATH/web/css/product-critical.css"
        },
        {
            "src": "/checkout/#shipping",
            "target": "app/design/frontend/THEMEPATH/THEMEPATH/web/css/checkout-critical.css"
        }
    ]
}

module.exports = {
    config,
    pages
}

In the pages array, src is the page you want critical css from and target is the place to drop the newly generated critical css bundle.

Dimensions only require widths (this differs per project). The height will be chosen based on a set of most used resolutions:

const standardViewports = [
    { width: 1920, height: 1080 },
    { width: 414, height: 896 },
    { width: 1536, height: 864 },
    { width: 1366, height: 768 },
    { width: 375, height: 667 },
    { width: 360, height: 640 },
];

If you want to explicitly use a set height, you may add it to the dimensions array like this (it will overwrite the default):

    "dimensions": [
       ...
        { "width": 767, "height": 3000 },
      ...
    ]

Running it

To use this package, you need to run: npx iodigital-criticalcss in the command line.

Using environment variables

There are some environment variables that can be used while generating the criticalcss.

Available environment variables

• DOMAIN: When domain is set, this will be used to render criticalcss for.
• CRITICALCSS_CONFIG_FILE: You can alter the criticalcss configuration file that will be used. Can be useful when deploying to more than one environment or to support multiple themes.

How to use environment variables

export DOMAIN=https://www.google.com
npx iodigital-criticalcss

or

DOMAIN=https://www.google.com npx iodigital-criticalcss