Example of HoC that check if user is authorised

AuthHoc.js

import React, { Component } from 'react';
import firebase from './firebase'

// Child is our Wrapped component
export default (Child) => (
  class AuthHoC extends Component {

    state = {
      isAuthenticated: false
    }

    componentDidMount() {
      // onAuthStateChanged return a function that we'll use to unsubscribe our listener
      this.unsubscribeMethod = firebase.auth().onAuthStateChanged(this._handleStateChange);
    }
    
    // is user is null, we're no longer authenticated
    _handleStateChange = (user) => {
      this.setState({
        isAuthenticated: !!user
      })

    }
  
    componentWillUnmount() {
      if(this.unsubscribeMethod) {
        this.unsubscribeMethod()
      }
    }

    render() {
      return <Child isAuthenticated={this.state.isAuthenticated} {...this.props} />
    }
})