Install

npm i -D posthtml-postcss

Usage

import {dirname} from 'node:path'
import {readFileSync} from 'node:fs'
import {fileURLToPath} from 'node:url'

import posthtml from 'posthtml'
import postcss from 'posthtml-postcss'

const postcssPlugins = []
const postcssOptions = {}
const filterType = /^text\/css$/

const __filename = fileURLToPath(import.meta.url)
const __dirname = dirname(__filename)

const filePath = `${__dirname}/index.html`
const html = readFileSync(filePath, 'utf8')

posthtml([ 
  postcss(postcssPlugins, postcssOptions, filterType) 
])
  .process(html, {from: filePath})
  .then((result) => console.log(result.html))

If you don't pass any arguments to posthtml-postcss, it will try to use your project's PostCSS configuration (see postcss-load-config).

Notice that we're setting the option from when calling process. posthtml-postcss forwards this to PostCSS, which is useful for syntax error messages. (postcss-cli and gulp-posthtml are setting from automatically.)

Example

import posthtml from 'posthtml'
import postcss from 'posthtml-postcss'
import autoprefixer from 'autoprefixer'

const postcssPlugins = [
  autoprefixer({ browsers: ['last 2 versions'] })
]
const postcssOptions = {}
const filterType = /^text\/css$/

const html = `
  <style>div { display: flex; }</style>
  <div style="display: flex;">Text</div>
`

posthtml([ 
  postcss(postcssPlugins, postcssOptions, filterType) 
])
  .process(html)
  .then(result => console.log(result.html))

Output:

<style>
  div { display: -webkit-flex;display: -ms-flexbox;display: flex; }
</style>
<div style="display: -webkit-flex;display: -ms-flexbox;display: flex;">
  Text
</div>