koa-socket's Introduction

Koa-socket

Sugar for connecting socket.io to a koa instance

Installation

npm i --save koa-socket

Example

var koa = require( 'koa' );
var socket = require( 'koa-socket' );

var app = koa();

app.use( ... );

socket.start( app );

socket.on( 'join', function( data ) {
  console.log( 'join event fired', data );
});

app.server.listen( process.env.PORT || 3000 );

Middleware and event handlers

Middleware can be added to sockets in much the same way as it is added to a koa instance.

var app = require( 'koa' )();
var socket = require( 'koa-socket' );

app.use( ... );

socket.use( function *( next ) {
  var start = new Date();

  yield next;
  console.log( 'elapsed:', new Date() - start );
});

socket.use( ... );

app.server.listen( 3000 );

Middleware context references both the data sent along with the socket event and the socket itself.

// From the client
socket.emit( 'event', {
  ua: navigator.userAgent,
  time: new Date()
});

// Listening on the server
socket.on( 'event', function( packet ) {
  // Id now exists on the packet thanks to middleware
  // Although in this trivial example it can be referenced on the context
  console.log( packet.id );
  console.log( this.id );
});

socket.use( function *( next ) {
  // This will fail
  console.log( this.data.id );

  yield next;

  // It'll work here though
  console.log( this.data.id );
});

socket.use( function *( next ) {
  this.data.id = this.socket.id;
});

In the above example the event handler will get executed after the middleware and the context is shifted so that this references the socket and its data is passed as the packet parameter.