Subscribe to Changes with Streaming API

The heart of the subscription mechanism is in the _subscribeChannels method in src/js/channel/ServerConnection.js.

cometd.subscribe(channelName, function(event) {
  if (event && event.data && event.data.payload && 
      event.data.payload.ChangeEventHeader) {
    var header = event.data.payload.ChangeEventHeader;
    var entityName = header.entityName;
    var recordId = header.recordIds[0];
    var timestamp = header.commitTimestamp;
    var changeType = header.changeType;
        
    switch (changeType) {
      case "UPDATE":
        // Update logic ...
        break;
     case "CREATE":
        // Create logic
        break;
     case "DELETE":
        // Delete logic
        break;
    }
  }
}

The channelName for Codey Outfitters’ products is /data/Products__ChangeEvent. Each change event notification that’s published on the channel is in the Bayeux format and represents an updated record in the product inventory. The data.payload contains the change event data and includes a header that describes the nature of the change event. This sample event notification describes a change to a Codey Outfitters product record.

{ 
  schema=”lswW55LyUCYeU7raSrmZ5A”,
  payload={
    ChangeEventHeader={
      commitUser=”005xx000001SvAn”, 
      sequenceNumber=15,
      entityName=”Products__x”,
      changeType=”UPDATE”, 
      changeOrigin=”Products?$deltaToken=3779”, 
      transactionKey=”f158f145-a...”, 
      commitTimestamp=1507759119826, 
      recordIds=[“x03xx0000000008”]
    },
    Name__c=”Camping Stove”,
    ExternalId=7801,
    UnitPrice__c=10.0,
    Stock__c=1500.0,
    OrderLimit__c=12.0,
    ProductId__c=7801.0
  },
  event={replayId=15}
}