How to Fix `createTheme_default is not a function` in Material UI

Fix: React Material UI createTheme_default is not a function

Introduction

If you're encountering the error:

Box.js:5 Uncaught TypeError: createTheme_default is not a function

when using Material UI with Vite in a React project, you're not alone. This error usually occurs due to import mismatches, caching issues, or incorrect dependency resolutions. This guide will walk you through the possible solutions.

Solution 1: Correct the Import Path

One common mistake is importing createTheme incorrectly. Instead of:

import { createTheme } from '@mui/material/styles'

Try this:

import createTheme from '@mui/material/styles/createTheme'

This ensures that the createTheme function is properly resolved.

Solution 2: Fix Import Order of Components

The order of Material UI component imports can sometimes cause issues in Vite. Ensure that CssBaseline and ThemeProvider are imported before Box:

Incorrect Import Order:

import Box from '@mui/material/Box'
import CssBaseline from '@mui/material/CssBaseline'

Correct Import Order:

import CssBaseline from '@mui/material/CssBaseline'
import Box from '@mui/material/Box'

This small change has resolved the issue for many developers.

Solution 3: Clear Vite Cache

Vite aggressively caches dependencies, which can cause issues even after rolling back changes. Try clearing the Vite cache by running:

rm -rf node_modules/.vite/deps && npm run dev

Alternatively, force a fresh build using:

npm run dev --force

If you're using Yarn:

yarn dev --force

Solution 4: Reinstall Material UI Dependencies

Sometimes, dependency mismatches cause this issue. A clean reinstall of Material UI can help:

npm uninstall @mui/material @emotion/react @emotion/styled
npm install @mui/material @emotion/react @emotion/styled

For Yarn users:

yarn remove @mui/material @emotion/react @emotion/styled
yarn add @mui/material @emotion/react @emotion/styled

Solution 5: Modify vite.config.js

If the issue persists, explicitly include Material UI in Vite's optimized dependencies in vite.config.js:

optimizeDeps: {
   include: ["@mui/material/Box"],
},

Solution 6: Wrap App in ThemeProvider

Ensure that the ThemeProvider is properly wrapping your application:

import { ThemeProvider, createTheme } from '@mui/material/styles'

const theme = createTheme({
  direction: 'rtl',
})

function App() {
  return (
    <ThemeProvider theme={theme}>
      <div className="App">Your components go here</div>
    </ThemeProvider>
  )
}

This ensures that theme properties are properly passed down to Material UI components.

FAQ

Why does Vite cause this issue?

Vite optimizes dependencies aggressively, sometimes leading to incorrect module resolution. Clearing the cache or explicitly defining dependencies can fix the issue.

Does this happen with Webpack?

No, Webpack has different dependency resolution mechanisms that typically avoid this issue.

Can I downgrade Material UI to fix this?

While downgrading may temporarily resolve the issue, it's best to follow the solutions above for a more sustainable fix.