naive.js

var App = require('./App')
var React = require('react')
var ReactDOM = require('react-dom')

// Render the root component normally
var rootEl = document.getElementById('root')
ReactDOM.render(<App />, rootEl)

// Are we in development mode?
if (module.hot) {
  // Whenever a new version of App.js is available
  module.hot.accept('./App', function () {
    // Require the new version and render it instead
    var NextApp = require('./App')
    ReactDOM.render(<NextApp />, rootEl)
  })
}

React Native version https://github.com/este/este/blob/0a7060827ba30fbaa8a8d19f03f82d5be0b7e689/src/native/app/Root.js#L56