reactjs - Change root background color with Material-UI theme

Question

I'm trying something very simple: building two themes for a website using Material-UI themes:

A light theme and dark one, but it does not work well: the theme is on every Material-UI react element, but the root element on the html document keeps having the same default white background.

Of course it can be changed by attacking the body with pure .css:

body {
  background-color: #222;
}

But I was looking to change it dynamically with React, I though this would work, but it does not:

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import { ThemeProvider } from '@material-ui/styles';
import { MuiThemeProvider, createMuiTheme } from '@material-ui/core/styles';

const themeLight = createMuiTheme({
  palette: {
    background: {
      default: "#e4f0e2"
    }
  },
});

const themeDark = createMuiTheme({
  palette: {
    background: {
      default: "#222222",
    }
  },
});

ReactDOM.render(
  <MuiThemeProvider theme = { themeDark }>
    <App />
  </MuiThemeProvider>, document.getElementById('root'));

and I'm lost here, there is no way to make this with Material-UI theme?

Answer 1

CssBaseline is the component that controls this aspect. If you aren't using CssBaseline, then you are just seeing the default provided by the browser.

Here is a working v4 example (v5 example further down):

import React from "react";
import ReactDOM from "react-dom";
import CssBaseline from "@material-ui/core/CssBaseline";
import { MuiThemeProvider, createMuiTheme } from "@material-ui/core/styles";
import Button from "@material-ui/core/Button";

const themeLight = createMuiTheme({
  palette: {
    background: {
      default: "#e4f0e2"
    }
  }
});

const themeDark = createMuiTheme({
  palette: {
    background: {
      default: "#222222"
    },
    text: {
      primary: "#ffffff"
    }
  }
});

const App = () => {
  const [light, setLight] = React.useState(true);
  return (
    <MuiThemeProvider theme={light ? themeLight : themeDark}>
      <CssBaseline />
      <Button onClick={() => setLight(prev => !prev)}>Toggle Theme</Button>
    </MuiThemeProvider>
  );
};

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

---

Below is a Material-UI v5 example. The only difference from v4 is the name change for ThemeProvider (though this name is also available in v4 in addition to MuiThemeProvider) and createTheme (instead of createMuiTheme) and using the new @mui/material package name instead of @material-ui/core.

import React from "react";
import ReactDOM from "react-dom";
import CssBaseline from "@mui/material/CssBaseline";
import { ThemeProvider, createTheme } from "@mui/material/styles";
import Button from "@mui/material/Button";

const themeLight = createTheme({
  palette: {
    background: {
      default: "#e4f0e2"
    }
  }
});

const themeDark = createTheme({
  palette: {
    background: {
      default: "#222222"
    },
    text: {
      primary: "#ffffff"
    }
  }
});

const App = () => {
  const [light, setLight] = React.useState(true);
  return (
    <ThemeProvider theme={light ? themeLight : themeDark}>
      <CssBaseline />
      <Button onClick={() => setLight((prev) => !prev)}>Toggle Theme</Button>
    </ThemeProvider>
  );
};

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);