import React from 'react'
import ReactDOM from 'react-dom'


class Doc extends React.Component{
  componentDidMount(){
    document.title = "dfsdfsdfsd"
  }

  render(){
    return(
      <b> test </b>
    )
  }
}

ReactDOM.render(
  <Doc />,
  document.getElementById('container')
);

This works for me.

Edit: If you're using webpack-dev-server set inline to true

You can use React Helmet:

import React from 'react'
import { Helmet } from 'react-helmet'

const TITLE = 'My Page Title'

class MyComponent extends React.PureComponent {
  render () {
    return (
      <>
        <Helmet>
          <title>{ TITLE }</title>
        </Helmet>
        ...
      </>
    )
  }
}

For React 16.8, you can do this with a functional component using useEffect.

For Example:

useEffect(() => {
   document.title = "new title"
}, []);

Having the second argument as an array calls useEffect only once, making it similar to componentDidMount.