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