client-lifecycle.js

import React, { Component } from 'react'
import io from 'socket.io-client'
import FontAwesome from 'react-fontawesome'
import Footer from './Footer'
import './App.css'
const API_URL = 'http://127.0.0.1:8080'
const socket = io(API_URL)

export default class App extends Component {

  constructor() {
    super()
    this.state = {
      user: {},
      disabled: ''
    }
    this.popup = null  
  }

  componentDidMount() {
    socket.on('user', user => {
      this.popup.close()
      this.setState({user})
    })
  }
  
  // Custom methods and render to follow
  // ....
}