just-styled
A dead simple CSS-in-JS library for React 19 or higher.
Features
- Familiar API: Both styled-components-like Styled Function and Style Prop are supported
- Typed Theme: Auto-completes your design token
- RSC Support: It just works. Nothing bothers you
- No Build Step: No need to set up build configuration
- Small Runtime: It's 1.8 kb minified & gzipped
- Atomic CSS: Generates optimized stylesheet to keep your distribution small
Installation
[!IMPORTANT] just-styled requires React 19 since it's based on React 19's stylesheet support. You can try it on Next.js 15 RC for now.
npm install just-styled
Usage
Styled Function
Creates your component with styled function.
import { styled } from "just-styled";
const StyledBox = styled("div", {
fontSize: "20px",
backgroundColor: "gray",
});
<StyledBox>The background is gray</StyledBox>;
Style Prop
Declares inline style with style prop.
<StyledBox style={{ color: "green" }}>The text color is green</StyledBox>
Box Component
We also have the built-in Box component as an equivalent of div.
import { Box } from "just-styled";
<Box style={{ fontSize: "100px" }}>Big text</Box>;
This is just a syntax sugar for the code below.
const Box = styled("div", {});
Nested Styles
You can nest styles with selectors such as pseudo classes.
const StyledBox = styled("div", {
backgroundColor: "gray",
":hover": {
backgroundColor: "black",
},
});
Also supports media queries and other at rules.
const StyledBox = styled("div", {
backgroundColor: "gray",
"@media (min-width: 768px)": {
backgroundColor: "black",
},
});
Theme
Create a config file anywhere you want. Currently colors, spaces, sizes, fontSizes, and radii tokens are supported.
import { defineConfig } from "just-styled";
export const config = defineConfig({
tokens: {
colors: {
"gray.200": "#eeeeee",
"gray.600": "#555555",
"red.200": "#EB7076",
"red.600": "#E02932",
primary: "$colors.red.600",
bg: "$colors.gray.200",
},
spaces: {
sm: "8px",
md: "16px",
},
},
});
// This is required for auto-completion
type UserConfig = typeof config;
declare module "just-styled" {
export interface JustStyledConfig extends UserConfig {}
}
Then, put ThemeProvider at the top of your component tree (e.g., layout.tsx on Next.js).
// import the config you defined
import { config } from "./theme-config.ts";
import { ThemeProvider } from "just-styled";
export default function RootLayout({
children,
}: Readonly<{ children: React.ReactNode }>) {
return (
<html lang="en">
<ThemeProvider config={config}>
<body>{children}</body>
</ThemeProvider>
</html>
);
}
Now, you can use your tokens with auto-completion.
const StyledBox = styled("div", {
backgroundColor: "$colors.bg",
padding: "$spaces.md",
});
<StyledBox style={{ color: "$colors.red.600" }}>Styled!</StyledBox>;