auth.js

require('dotenv').config()

exports.handler = function(event, context, callback) {
  let query = event.queryStringParameters

  let Pusher = require('pusher')
  let pusher = new Pusher({
    appId: process.env.PUSHER_APP_ID,
    key: process.env.PUSHER_KEY,
    secret: process.env.PUSHER_SECRET,
    cluster: process.env.PUSHER_CLUSTER,
    useTLS: true
  })

  let presenceData = {
    user_id: query.socket_id,
    user_info: {
      name: query.username
    }
  }

  let auth = JSON.stringify(pusher.authenticate(query.socket_id, query.channel_name, presenceData))
  let authCallback = query.callback.replace(/\"/g,"") + "(" + auth + ");"

  callback(null, {
    statusCode: 200,
    headers: {
      'Content-Type': 'application/javascript',
    },
    body: authCallback,
  })
}