extract-css-core

extract-css-core

Extract all CSS from a given url, both server side and client side rendered.

Problem, solution and shortcomings

Problem

Existing packages like get-css look at a server-generated piece of HTML and get all the <link> and <style> tags from it. This works fine for 100% server rendered pages, but apps that employ style injection with JavaScript will not be covered.

Solution

This module uses an instance of Chromium to render a page. This has the benefit that most of the styles can be rendered, even when generated by JavaScript. The Puppeteer CSSCoverage API is the power behind finding most of the CSS.

Shortcomings

Currently, there is no solution to get the CSS from modules that use Styled Components or something similar. Any help resolving this issue will be very much appreciated. Please contribute to the relevant GitHub issue.

Installation

npm install extract-css-core

# Or with Yarn
yarn add extract-css-core

Usage

const extractCss = require('extract-css-core')

extractCss('http://www.projectwallace.com').then(css => console.log(css))

API

extractCss(url, [options])

Extract CSS from a page. Returns a Promise that contains the CSS as a single String.

Options

Type: Object

Default: null

debug

Type: Boolean

Default: false

Set to true if you want a Chromium window to open as it works to get all the CSS from the page.

waitUntil

Type: String

Default: networkidle2

Can be any value as provided by the Puppeteer docs.

browserOverride

Type: Object

Default: null

An object consisting of the following fields:

• executablePath: the path to a Chromium binary
• puppeteer: a Puppeteer instance
• args: arguments to start Chromium with

See the test directory for implementation examples. This option exists primarily for use with extract-css.now.sh

Related

• extract-css lambda - Extract CSS running as a serverless function
• get-css - The original get-css