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@Merott
Last active February 23, 2024 00:22
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Expose Tailwind colors as CSS custom properties (variables)

This is a simple Tailwind plugin to expose all of Tailwind's colors, including any custom ones, as custom css properties on the :root element.

There are a couple of main reasons this is helpful:

  • You can reference all of Tailwind's colors—including any custom ones you define—from handwritten CSS code.
  • You can define all of your colors within the Tailwind configuration, and access the final values programmatically, which isn't possible if you did it the other way around: referencing custom CSS variables (defined in CSS code) from your Tailwind config.

See the Tailwind Plugins for more info on plugins.

module.exports = {
  theme: {
    extend: {
      colors: {
        gray: {
          '100': '#f5f5f5',
          '200': '#eeeeee',
          '300': '#e0e0e0',
          '400': '#bdbdbd',
          '500': '#9e9e9e',
          '600': '#757575',
          '700': '#616161',
          '800': '#424242',
          '900': '#212121',
        },
      },
    },
  },
  plugins: [
    function({ addBase, theme }) {
      function extractColorVars(colorObj, colorGroup = '') {
        return Object.keys(colorObj).reduce((vars, colorKey) => {
          const value = colorObj[colorKey];

          const newVars =
            typeof value === 'string'
              ? { [`--color${colorGroup}-${colorKey}`]: value }
              : extractColorVars(value, `-${colorKey}`);

          return { ...vars, ...newVars };
        }, {});
      }

      addBase({
        ':root': extractColorVars(theme('colors')),
      });
    },
  ],
};
@ianhernandez
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Anyone have a typescript version of this?

@y-nk
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y-nk commented Aug 19, 2023 via email

@mathieutu
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mathieutu commented Sep 5, 2023

I works like a charm in Tailwind v3.3.3, thanks! 🎉

Here is a TS simplified version:

import { type PluginAPI } from 'tailwindcss/types/config'

export const colorVarsPlugin = ({ addBase, theme }: PluginAPI) => {
  const extractColorVars = (colorObj: Record<string, string>, colorGroup = '') => (
    Object.entries(colorObj)
      .reduce((vars, [colorKey, value]) => {
        const cssVariable = colorKey === 'DEFAULT' ? `--color${colorGroup}` : `--color${colorGroup}-${colorKey}`

        const newVars: Record<string, string> = typeof value === 'string'
          ? { [cssVariable]: value }
          : extractColorVars(value, `-${colorKey}`)

        return { ...vars, ...newVars }
      }, {})
  )

  addBase({
    ':root': extractColorVars(theme('colors')),
  })
}

EDIT: Indeed, it'd be great to find a way to purge the colors..

@joshdavenport
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joshdavenport commented Oct 18, 2023

A note to people stumbling on this gist as I did: This plugin is awesome, really nice idea, but consider adding variables to your CSS manually. Using something like the below, as long as you have access in your CSS to tailwind directives, you can reference colours and create variables from them:

:root {
  --tw-color-white: theme('colors.white');
  --tw-color-black: theme('colors.black');
  --tw-color-gray-100: theme('colors.gray.100');
  --tw-color-gray-200: theme('colors.gray.200');
  --tw-color-gray-300: theme('colors.gray.300');
  --tw-color-gray-400: theme('colors.gray.400');
  --tw-color-gray-500: theme('colors.gray.500');
  --tw-color-gray-600: theme('colors.gray.600');
  --tw-color-gray-700: theme('colors.gray.700');
  --tw-color-gray-800: theme('colors.gray.800');
  --tw-color-gray-900: theme('colors.gray.900');
  --tw-color-gray-950: theme('colors.gray.950');
}

For example, if you're using Next and following the globals.css pattern the docs describe you can add this to globals.css.

Doing it that way you don't need to worry about the bundle size reports others have mentioned (haven't looked at it myself, so no idea how badly it affects the size). Obviously the whole point of the plugin is quickly and easily provide access to all colours, but maybe you don't need that, so consider what you need contextually.

@oskarengstrom
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oskarengstrom commented Nov 29, 2023

A note to people stumbling on this gist as I did: This plugin is awesome, really nice idea, but consider adding variables to your CSS manually. Using something like the below, as long as you have access in your CSS to tailwind directives, you can reference colours and create variables from them:

@joshdavenport
This sounds great, but exactly how do you use theme() in globals.css?

@simonhamp
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@oskarengstrom if you're generating your CSS through a bundler, like Vite or Webpack, then the theme() function will be exposed to you.

It won't work in plain CSS

@rafaelrcamargo
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That's great! If anyone wants, here is a version that exports "R, G, B" values so you can use RGBA and play with the alpha in CSS:

import type { PluginAPI } from "tailwindcss/types/config"

export const colorsToVars = ({ addBase, theme }: PluginAPI) => {
  const extractColorVars = (
    colorObj: Record<string, string>,
    colorGroup = ""
  ) =>
    Object.entries(colorObj).reduce((vars, [colorKey, value]) => {
      const cssVariable =
        colorKey === "DEFAULT"
          ? `--tw${colorGroup}`
          : `--tw${colorGroup}-${colorKey}`

      const newVars: Record<string, string> =
        typeof value === "string"
          ? { [cssVariable]: parseColor(value)?.color.join(", ") }
          : extractColorVars(value, `-${colorKey}`)

      return { ...vars, ...newVars }
    }, {})

  addBase({ ":root": extractColorVars(theme("colors")) })
}

/**
 * Color Parser
 * Grabbed this from Tailwind's source code :)
 */

let HEX = /^#([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})?$/i
let SHORT_HEX = /^#([a-f\d])([a-f\d])([a-f\d])([a-f\d])?$/i
let VALUE = /(?:\d+|\d*\.\d+)%?/
let SEP = /(?:\s*,\s*|\s+)/
let ALPHA_SEP = /\s*[,/]\s*/
let CUSTOM_PROPERTY = /var\(--(?:[^ )]*?)(?:,(?:[^ )]*?|var\(--[^ )]*?\)))?\)/

let RGB = new RegExp(
  `^(rgba?)\\(\\s*(${VALUE.source}|${CUSTOM_PROPERTY.source})(?:${SEP.source}(${VALUE.source}|${CUSTOM_PROPERTY.source}))?(?:${SEP.source}(${VALUE.source}|${CUSTOM_PROPERTY.source}))?(?:${ALPHA_SEP.source}(${VALUE.source}|${CUSTOM_PROPERTY.source}))?\\s*\\)$`
)
let HSL = new RegExp(
  `^(hsla?)\\(\\s*((?:${VALUE.source})(?:deg|rad|grad|turn)?|${CUSTOM_PROPERTY.source})(?:${SEP.source}(${VALUE.source}|${CUSTOM_PROPERTY.source}))?(?:${SEP.source}(${VALUE.source}|${CUSTOM_PROPERTY.source}))?(?:${ALPHA_SEP.source}(${VALUE.source}|${CUSTOM_PROPERTY.source}))?\\s*\\)$`
)

export function parseColor(value: string, { loose = false } = {}) {
  value = value.trim()

  let hex = value
    .replace(SHORT_HEX, (_, r, g, b, a) =>
      ["#", r, r, g, g, b, b, a ? a + a : ""].join("")
    )
    .match(HEX)

  if (hex !== null) {
    return {
      mode: "rgb",
      color: [
        parseInt(hex[1]!, 16),
        parseInt(hex[2]!, 16),
        parseInt(hex[3]!, 16)
      ].map(v => v.toString()),
      alpha: hex[4] ? (parseInt(hex[4], 16) / 255).toString() : undefined
    }
  }

  let match = value.match(RGB) ?? value.match(HSL)
  if (match === null) return null

  let color = [match[2], match[3], match[4]]
    .filter(Boolean)
    .map(v => v!.toString())

  if (color.length === 2 && color[0]!.startsWith("var("))
    return { mode: match[1], color: [color[0]], alpha: color[1] }

  if (!loose && color.length !== 3) return null

  if (color.length < 3 && !color.some(part => /^var\(.*?\)$/.test(part)))
    return null

  return { mode: match[1], color, alpha: match[5]?.toString?.() }
}

The variables will be in "R, G, B" format so you can use them as follows:

  fill: rgba(var(--tw-green-500), 0.8);

@GeorgeCht
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If anyone is still interested for a plugin on this check @tailwind-plugin/expose-colors.

@Merott
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Author

Merott commented Jan 9, 2024

I wish we had reaction emojis in gists!

Just wanted to say I ❤️ all the ways in which this little snippet (that I'm no longer even using myself) has been adapted! 😁

@sudo-vaibhav
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@Merott +1, glad to have been among the first people who contributed to this gist, and see what twisted new creative ways people have extended it. I come back to it every 6 months to see what has become of this gist.

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