Using FontFaceObserver for React app loader

App.js

import React from 'react'
import 'fontfaceobserver'
import IndexPage from './IndexPage'
import Loader from './Loader'

import { fetchUser } from '../apiclient'

import 'font-awesome-webpack'
import './Lato-font.css'
import './Roboto-font.css'

export default class App extends React.Component {
  constructor () {
    super()
    this.state = {
      isLoading: true
    }

    Promise.all([
      fetchUser(),
      new FontFaceObserver('Roboto').check(),
      new FontFaceObserver('Lato').check(),
      new FontFaceObserver('FontAwesome').check('\u{F135}'),
      new FontFaceObserver('Glyphicons Halflings').check('\u{E104}') // included here for demonstration purposes
    ]).then(([user]) => {
      this.setState({isLoading: false, user})
    }, err => {
      console.error('Failed to load fonts!', err)
      this.setState({isLoading: false})
    })
  }

  render () {
    const { isLoading, user } = this.state
    return (
      isLoading
        ? <Loader/>
        : <IndexPage user={user}/>
    )
  }
}

package.json

{
  "private": true,
  "dependencies": {
    "font-awesome": "^4.4.0",
    "font-awesome-webpack": "0.0.4",
    "fontfaceobserver": "^1.5.4",
    "react": "^0.14.1",
    "react-dom": "^0.14.1"
  }
}