use-system-theme
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React Hook for System Theme
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# use-system-theme
[](https://www.npmjs.com/package/use-system-theme)
[](https://circleci.com/gh/xcv58/use-system-theme)
[](https://codeclimate.com/github/xcv58/use-system-theme/maintainability)
React Hook for System Theme (User preferred color scheme). Please use React `> 16.8.0` for React Hooks support.
It detects the system theme and will update right after the users change the theme.
## Install
```bash
yarn add use-system-theme
```
or
```bash
npm install --save use-system-theme
```
## Usage
```tsx
import React from 'react'
import useSystemTheme from 'use-system-theme'
export default () => {
const systemTheme = useSystemTheme()
return <div>The System Theme is: {systemTheme}</div>
}
```
## Browser support
As 2019 December, all major browsers on both mobile and desktop platforms support the `prefers-color-scheme media query` feature. For more details, please check:
[https://caniuse.com/#feat=prefers-color-scheme](https://caniuse.com/#feat=prefers-color-scheme)
## SSR support
The `useSystemTheme` function has only one argument `isSSR`, and you must pass `true` for SSR app. Otherwise, your app may have bug like doesn't show dark them on dark theme devices.
```tsx
declare const useSystemTheme: (isSSR?: boolean) => SystemTheme
```
```tsx
import React from 'react'
import useSystemTheme from 'use-system-theme'
export default () => {
const systemTheme = useSystemTheme(true)
return <div>The System Theme is: {systemTheme}</div>
}
```
To support SSR (server side rendering), the initial theme will be always `light` (since we don't know the theme on the server side) and it would immediately become `dark` if the device's theme is `dark`. Unfortunately, we can't avoid this because of the [React hydrate](https://reactjs.org/docs/react-dom.html#hydrate):
> React expects that the rendered content is identical between the server and the client.
So that for all SSR app, the initial screen will be `light` and become `dark` immediately on dark theme devices. It's caused by the nature of how React SSR works.
## Development
`yarn start`
To build the library and watch the file changes locally.
### Develop with local examples
The local examples use the [yalc](https://github.com/whitecolor/yalc) to get live local version library.
You need to run `yarn watch:yalc` on the root directory during development. And use `npx yalc add use-system-theme` in the example directory under `examples/`. Then follow the README file in each example folder.
Note: the `yalc` will change the `pcakge.json` for the example project to `"use-system-theme": "file:.yalc/use-system-theme"`. Please do **NOT** commit the change because it would cause CI/CD failure.
## License
MIT © [xcv58](https://github.com/xcv58)