Implementing Socket.io with ReactJS ES6

- 1 answer

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I'm having trouble incorporating SocketIO client into my project as I have me project set up isomorphically. After including the socket file in my base html, I try to call let socket = io(); in the componentdidmount of one of my components however initially after logging it in my console it is undefined. When I route to a different component and comeback to that component with that socket variable then it becomes filled with some data. I guess my point here it isn't initializing in my component what socket is, it seems like it has to wait how do I work around this?

Component.jsx

componentDidMount() {
    let socket = io();
    console.log(socket);
  }

Base.html

<!doctype html>
<html lang="">

<head>
    <title>TITLE</title>

    META

    LINK

</head>

<div class="app">CONTENT</div>

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<script>
    (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
        (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
            m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
    })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
    ga('create', 'UA-XXXXX-X', 'auto');
    ga('send', 'pageview');
</script>
<script type="text/javascript" charset="utf-8" src="/assets/app.js"></script>

<script src="/socket.io/socket.io.js"></script>
<script>
        var socket = io();
</script>

</body>
</html>

This works fine btw I for stuff like on connect from the server, it emits that a user is connecting and disconnecting off the server, just the client manipulation has me puzzled.

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Answer

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There are likely other solutions, but the following works for me:

1) npm install the socket client side package

2) import socket into the most root component of all components that need socket functionality

3) hookup server side socket event listeners in one of the lifecycle events (constructor / componentWillMount, componentDidMount)

4) pass down socket object through props if it makes sense to handle certain server events in child components

example:

import io from 'socket.io-client'
let socket = io(`http://localhost:8000`)

class App extends Component {
  state = { data: {} }

  componentDidMount() {    
    socket.on(`server:event`, data => {
      this.setState({ data })
    })
  }

  sendMessage = message => {
    socket.emit(`client:sendMessage`, message)
  }

  render () {
    return (
      <Child 
        socket = { socket } 
        sendMessage = { this.sendMessage }
      />
    )
  }
}
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source: stackoverflow.com
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