Responsive Variants with CVA, class-variance-authority

1. useResponsiveVariant.ts

import { useMediaQuery } from 'usehooks-ts'
import { useMemo } from 'react';
import { screens } from '.generated/screens';

/* 
// You can also define the screens object manually if you don't want to use a prebuilt script.

const screens = {
  sm: '640px',
  md: '768px',
  lg: '1024px',
  xl: '1280px',
  '2xl': '1536px',
} as const;
*/

type Breakpoints = keyof typeof screens;

type ResponsiveValue<T> = T extends boolean ? boolean : T extends string ? T : keyof T;

type ResponsiveProps<T> = {
  [K in Breakpoints]?: ResponsiveValue<T>;
} & { initial: ResponsiveValue<T> };

function getScreenValue(key: string) {
  return Number.parseInt(screens[key as Breakpoints].replace('px', ''), 10);
}

/**
 * Custom hook for handling responsive behavior based on breakpoints.
 * @param props - The responsive props containing breakpoints and initial value.
 * @returns The responsive value based on the current breakpoint.
 */
export function useResponsiveVariant<T>(props: ResponsiveProps<T>) {
  const { initial, ...breakpoints } = props;

  const mediaQueries = Object.keys(breakpoints)
    .sort((a, b) => getScreenValue(b) - getScreenValue(a))
    .map((breakpoint) =>
      useMediaQuery(`(min-width: ${screens[breakpoint as Breakpoint]})`)
        ? breakpoints[breakpoint as Breakpoint]
        : undefined
    )
    .filter((value) => value !== undefined);

  const size = useMemo(() => {
    return mediaQueries[0] ?? initial;
  }, [initial, mediaQueries]);

  return size as ResponsiveValue<T>;
}

2. Button.tsx

import * as React from "react"
import { Slot } from "@radix-ui/react-slot"
import { cva, type VariantProps } from "class-variance-authority"

import { cn } from "@/lib/utils"

const buttonVariants = cva(
  "inline-flex items-center justify-center whitespace-nowrap rounded-md text-sm font-medium ring-offset-background transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50",
  {
    variants: {
      variant: {
        default: "bg-primary text-primary-foreground hover:bg-primary/90",
        destructive:
          "bg-destructive text-destructive-foreground hover:bg-destructive/90",
        outline:
          "border border-input bg-background hover:bg-accent hover:text-accent-foreground",
        secondary:
          "bg-secondary text-secondary-foreground hover:bg-secondary/80",
        ghost: "hover:bg-accent hover:text-accent-foreground",
        link: "text-primary underline-offset-4 hover:underline",
      },
      size: {
        default: "h-10 px-4 py-2",
        sm: "h-9 rounded-md px-3",
        lg: "h-11 rounded-md px-8",
        icon: "h-10 w-10",
      },
    },
    defaultVariants: {
      variant: "default",
      size: "default",
    },
  }
)

export interface ButtonProps
  extends React.ButtonHTMLAttributes<HTMLButtonElement>,
    VariantProps<typeof buttonVariants> {
  asChild?: boolean
}

const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
  ({ className, variant, size, asChild = false, ...props }, ref) => {
    const Comp = asChild ? Slot : "button"
    return (
      <Comp
        className={cn(buttonVariants({ variant, size, className }))}
        ref={ref}
        {...props}
      />
    )
  }
)
Button.displayName = "Button"

export { Button, buttonVariants }

3. Example.tsx

import { Button, ButtonProps } from '@/ui';

function Example() {
  const buttonSize = useResponsiveVariant<ButtonProps['size']>({ initial: 'sm', sm: 'lg' });

  return <Button size={buttonSize}>Button</Button>
}

4. prebuild.ts

import fs from 'node:fs';
import path from 'node:path';

import resolveConfig from 'tailwindcss/resolveConfig';
import tailwindConfig from './tailwind.config';

const fullConfig = resolveConfig(tailwindConfig);

const screens = `export const screens = ${JSON.stringify(
  fullConfig.theme.screens,
  null,
  2
)} as const;`;

// Make sure the folder exists
if (!fs.existsSync(path.join(__dirname, './src/.generated'))) {
  fs.mkdirSync(path.join(__dirname, './src/.generated'));
}

fs.writeFileSync(path.join(__dirname, './src/.generated/screens.ts'), screens, 'utf8');

Great solution, thanks!

Great solution, thanks!

@mnzsss You're welcome, I made a quick revision as it wasn't fully working with boolean values ✌️

Actually, using resolveConfig will transitively pull in a lot of our build-time dependencies, resulting in bigger client-side bundle size, as stated here: https://tailwindcss.com/docs/configuration#referencing-in-java-script

I added a prebuild script, screens can also be hardcoded