sass-to-string is a set of helper tools that allow your Web application to leverage SASS files as JavaScript strings so you can use them the way you want afterwards. This is especially useful for Web Components that need to inject their stylesheets directly in the template.

sass-to-string provides two different approaches

• A Webpack loader that transforms SASS files to native JavaScript strings
• A sass-to-string command that transforms your scss files to a native JavaScript string at build time

First install the module with your favorite loader

# With NPM
npm install sass-to-string --save-dev
# With Yarn
yarn install sass-to-string -D

In your webpack.config.js, add the following rule.

module.exports = {
  module: {
    rules: [
      {
        test: /\.styles.scss$/,
        exclude: /node_modules/,
        use: [
          "sass-to-string",
          {
            loader: "sass-loader",
            options: {
              sassOptions: {
                outputStyle: "compressed",
              },
            },
          },
        ],
      },
    ],
  },
};

Chances are you already have a SASS config in your webpack config and the above code just broke it. To fix this, add .styles.scss in the exclude of the rule.

See the exclude part in the following example

module.exports = {
  module: {
    rules: [
      {
          // Your new shiny sass-to-string config
      },
      {
        test: /\.(scss|css)$/,
        // Excluding the `.styles.scss` extension
        exclude: [/\.styles.scss$/, /node_modules/],
        use: [
          "style-loader",
          MiniCssExtractPlugin.loader,
          "css-loader",
          {
            loader: "sass-loader",
          },
        ],
      },
    ];
  }
}

Now that Webpack is configured, you can access your compiled SCSS code in a JS module.

Say we have this SCSS

section {
  p {
    font-family: "Comic Sans MS";
  }
}

sass-loader will resolve it to this value:

section p {
  font-family: "Comic Sans MS";
}

Awesome! Not let's pull this in a tractor.js javascript module

import styles from "./tractor.styles.scss";

// Outputs : section p{font-family:"Comic Sans MS"}
console.log(styles);

The motivation behind this package was to be able to use SASS inside Web Components. Here's an example of doing such

import styles from "./tractor.styles.scss";

class TractorViewer extends HTMLElement {
  constructor() {
    super();

    const style = document.createElement("style");
    // styles equals "section p{font-family:"Comic Sans MS"}"
    style.textContent = styles;

    const shadowRoot = this.attachShadow({ mode: "open" });
    shadowRoot.appendChild(style);
  }
}

Note that this module needs webpack and the magic from sass-loader in order to do its job properly

If you face typings errors in your IDE, add this line to your local typings file

import "sass-to-string/index";

// Any other type declarations you might have

It should solve the IDE error

We also expose a sass-to-string command that will transform your SASS files in a JavaScript string. Here's a quick example.

Pretend you have this SCSS file called demo.styles.scss

body {
  p {
    color: red;
  }
}

And this JavaScript import statement alongside

import styles from "./demo.styles.scss";

When running the command, it'll create a demo.styles.scss.js file in the right directory under dist.

const styles = `body p {
  color: red;
}`;
export default styles;

As you guessed it, you can run it alongside tsc a fully working app using SASS and only bundled with Typescript.

Here's an example on how you could run a build command in your package.json

{
  "scripts": {
    ...
    "build": "tsc && sass-to-string"
  }
}

You can also provide some command options to sass-to-string like such

{
  "scripts": {
    ...
    "build": "sass-to-string --dist=lib"
  }
}

If you prefer, you can also create a .sass-to-string.js file at the root of your project

module.exports = {
  dist: "lib",
  // Replaces bootstrap imports by resolving node_modules
  prepare: (scss) =>
    scss.replace(/@import "bootstrap/g, `@import "node_modules/bootstrap`),
};

Note that this module requires a peerDependency on fs-extra and sass in order to work properly

Of course you do! Thinking and coding this package implied quite a lot of coffee. If you want, you can buy me one! ☕️