Can I create a custom class with arbitrary values Tailwindcss

Question

I want to create a class in Tailwindcss with arbitrary values for example

HTML

<button class="my-custom-class[#fff]" />

CSS

@layer componenets {
  .my-custom-class {
    @apply bg-[--here-arbitrary-value]; /** the value is #fff */
  }
}

Answer 1

You can but not using layer components

You need to write simple plugin for that

tailwind.config.js

const plugin = require('tailwindcss/plugin')
const flattenColorPalette = require('tailwindcss/lib/util/flattenColorPalette')

module.exports = {
  theme: {
    extend: {
      colors: {
        from: {
          config: {
            500: 'yellow', // for example purposes
          },
        },
      },
    },
  },
  plugins: [
    plugin(function ({ matchUtilities, theme }) {
      matchUtilities(
        {
           // Class name
          'my-custom-class': (value) => {
            return {
              backgroundColor: value, // Desired CSS properties here
              color: theme('colors.white') // Just for example non-dynamic value
            }
          },
        },
        // Default values.
        // `flattenColorPalette` required to support native Tailwind color classes like `red-500`, `amber-300`, etc. 
        // In most cases you may just pass `theme('config-key')`, where `config-key` could be any (`spacing`, `fontFamily`, `foo`, `bar`)
        { values: flattenColorPalette(theme('colors')) } 
      )
    }),
  ],
}

Now you can use it like

<div class="my-custom-class-[#000] my-4 p-6">JIT as HEX</div>

<div class="my-custom-class-[red] my-4 p-6">JIT as string</div>

<div class="my-custom-class-[rgb(0,0,0)] my-4 p-6">JIT as RGB</div>

<div class="my-custom-class-blue-500 my-4 p-6">Using Tailwind Colors</div>

<div class="my-custom-class-from-config-500 my-4 p-6 text-black">Using extended colors from config. NOTE: `text-black` doesn't applied!</div>

NOTE: your class will take precedence over basic Tailwind classes

<div class="bg-red-500 my-custom-class-[yellow]">
  This has yellow background
</div>

More about writing plugins here

DEMO