[Rails] syntax error in react file index.js

[fugee ohu]

app/javascript/packs/index.js

import React from 'react'
import ReactDom from 'react-dom'
import App from '../components/App'

document.addEventListener('DOMContentLoaded', () => {
   ReactDom.render(
      <App/>,
      document.body.appendChild(document.createElement('div')),
   )
})   

I get this error:
SyntaxError: .../packs/index.js: Unexpected token (7:6)

    5 | document.addEventListener('DOMContentLoaded', () => {
    6 |    ReactDom.render(
>  7 |       <App/>,
       |       ^

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