CSS Var Extract

Use CSS variables type-safely for CSS-in-JS.

Generate at build time, has no runtime dependencies, and can be optimized.

🤔 Why?

Type-safely access CSS variables created by yourself or by external component libraries from TypeScript.

:root {
    --primary: #d3a3a3;
    --secondary: #5aa68a;
    --white: #fff;
}

Automatically generate .ts files based on .css.

// :root: #d3a3a3
export const primary = "var(--primary)"

// :root: #5aa68a
export const secondary = "var(--secondary)"

// :root: #fff
export const white = "var(--white)"

It can be used in styles and also in CSS-in-JS such as vanilla-extract.

import "./theme.css";
import * as vars from "./cssVar.gen";

const App = () => {
    return (
        <div style={{ backgroundColor: vars.primary }}>
            <h1 style={{ color: vars.primary }}>
                Primary color
            </h1>
            <p style={{ color: vars.secondary }}>
                Secondary color
            </p>
        </div>
    );
};

export default App;

import { style } from "@vanilla-extract/css";
import * as vars from "./cssVar.gen.ts";

export const buttonStyle = style({
    backgroundColor: vars.primary,
});

export const messageStyle = style({
    color: vars.secondary,
});

📦 Installation

You need to configure your project's bundler to use the CssVarExtract Plugin or the CssVarExtract CLI.

The plugin will automatically generate .ts through your bundler's dev and build processes.

Configuration with Vite

• examples/basic-vite-react
• examples/with-vanilla-extract

You need to install the css-var-extract-plugin package.

npm i -D css-var-extract-plugin

Once installed, you'll need to add the plugin to your Vite configuration.

// vite.config.ts
import react from "@vitejs/plugin-react";
import CssVarExtractVite from "css-var-extract-plugin/vite";
import { defineConfig } from "vite";

export default defineConfig({
    plugins: [
        CssVarExtractVite({
            files: ["src/theme.css"],
        }),
        react(),
    ],
});

Configuration with Rspack/Rsbuild

• examples/basic-rsbuild-react

You need to install the css-var-extract-plugin package.

npm i -D css-var-extract-plugin

Once installed, you'll need to add the plugin to your configuration.

// rsbuild.config.ts
import { defineConfig } from "@rsbuild/core";
import { pluginReact } from "@rsbuild/plugin-react";
import CssVarExtractRspack from "css-var-extract-plugin/rspack";

export default defineConfig({
    plugins: [pluginReact()],
    tools: {
        rspack: {
            plugins: [
                CssVarExtractRspack({
                    files: ["src/theme.css"],
                }),
            ],
        },
    },
});

Configuration with Webpack

• examples/basic-webpack-react

You need to install the css-var-extract-plugin package.

npm i -D css-var-extract-plugin

Once installed, you'll need to add the plugin to your configuration.

// webpack.config.ts
import CssVarExtractWebpack from "css-var-extract-plugin/webpack"

export default {
    plugins: [CssVarExtractWebpack({
        files: ["src/theme.css"],
    })],
}

Configuration with the CSS Var Extract CLI

You need to install the css-var-extract-cli package.

npm i -D css-var-extract-cli

Once installed, you'll need to amend your scripts in your package.json for the CLI to watch and generate files.

{
  "scripts": {
    "generate-css-var": "cve generate",
    "watch-css-var": "cve watch",
    "build": "npm run generate-css-var && ...",
    "dev": "npm run watch-css-var && ..."
  }
}

With the CLI installed, the following commands are made available via the cve command

Using the generate command

Generates the .ts file based on the provided configuration.

cve generate

Using the watch command

Continuously watches the specified files and regenerates the .ts file as needed.

cve watch

🔧 Configuration

You can create cve.config.json and change settings. If you are using a plugin, it also supports inline configuration.

You can also override the settings by the CVE_CONFIG environment variable.

Priority

The lower the number, the higher the priority.

1. Environment variable: CVE_CONFIG
2. Inline config
3. File config cve.config.json

JSON

{
  "files": [],
  "output": "./src/cssVar.gen.ts",
  "fileHeader": [
    "/* prettier-ignore-start */",
    "/* eslint-disable */",
    "// @ts-nocheck",
    "// noinspection JSUnusedGlobalSymbols"
  ],
  "fileFooter": [
    "/* prettier-ignore-end */"
  ],
  "disableLogging": false,
  "emoji": true
}

Option	Description
files	CSS files that collects css variables. Set relative or absolute path.
output	Path to generate the Typescript file. Set relative or absolute path.
fileHeader	Header of the generated file.
fileFooter	Footer of the generated file.
disableLogging	Disable logging on generation.
emoji	Use emojis in logs.

👏 Acknowledgments

This project was inspired by and references implementation patterns from the TanStack Router package. We extend our gratitude to the developers and maintainers of TanStack Router for their excellent work.