lit-css-loader

lit-css-loader

Webpack loader to import css files as JavaScript tagged-template literal objects.

The "Lit" stands for "Literal"

You can use it to import CSS for various libraries like lit-element, @microsoft/fast-element, or others.

Do I Need This?

No. This is an optional package who's sole purpose is to make it easier to write CSS-in-CSS while working on lit-element projects. You can just as easily write your CSS in some 'styles.css.js' modules a la:

import { css } from 'lit-element';
export default css`:host { display: block; }`;

And this may actually be preferred.

Hopefully this package will become quickly obsolete when the CSS Modules Proposal (or something like it) is accepted and implemented.

In the mean time, enjoy importing your CSS into your component files.

Options

Name	Accepts	Default
include	Array of glob of files to include.	['**/*.css']
exclude	Array of glob of files to exclude.	undefined
cssnano	Boolean or Object of cssnano options.	false
specifier	Package to import css from	lit
tag	Name of the template-tag function	css
transform	Optional function (sync or async) which transforms css sources (e.g. postcss)	x => x

Usage

npm i -D lit-css-loader

module: {
  rules: [
    {
      test: /\.css$/,
      loader: 'lit-css-loader',
      options: {
        specifier: 'lit-element' // defaults to `lit`
      }
    }
  ]
}

import { LitElement, html } from 'lit';
import { customElement } from 'lit/decorators.js';

import style from './styled-el.css';

@customElement('styled-el')
export class extends LitElement {
  static styles = [style]
  render() {
    return html`<p>such style. very win</p>`;
  }
}

Usage with Sass, Less, PostCSS, etc.

To load scss files:

1. Adjust the test clause of the module rule as needed (e.g)
2. Pass a transform function to the loader options

const Sass = require('sass');
module.exports = {
  module: {
    rules: [
      {
        test: /\.scss$/,
        loader: 'lit-css-loader',
        options: {
          transform: (data, { filePath }) =>
            Sass.renderSync({ data, file: filePath })
              .css.toString(),
        }
      }
    ]
  }
}

Similarly, to transform sources using PostCSS, specify a transform function:

const postcss = require('postcss');
const postcssNesting = require('postcss-nesting');

const processor = postcss(postcssNesting());

module.exports = {
  module: {
    rules: [
      {
        test: /\.scss$/,
        loader: 'lit-css-loader',
        options: {
          transform: (css, { filePath }) =>
            processor.process(css, { from: filePath })
              .css
        }
      }
    ]
  }
}

Looking for rollup? rollup-plugin-lit-css Looking for esbuild? esbuild-plugin-lit-css Looking for typescript? typescript-transform-lit-css