app.js
/*
 * Message Read Event
 *
 * This event is called when a previously-sent message has been read.
 * https://developers.facebook.com/docs/messenger-platform/webhook-reference/message-read
 * 
 */
Message Read Event
This event is called when a previously-sent message has been read.
Message Read Event This event is called when a previously - sent message has been read .
function receivedMessageRead(event) {
	var senderID = event.sender.id;
	var recipientID = event.recipient.id;
	var watermark = event.read.watermark;
	var sequenceNumber = event.read.seq;
	console.log("Received message read event for watermark %d and sequence " +
		"number %d", watermark, sequenceNumber);
}
function receivedMessageRead ( event ) { var senderID = event . sender . id ; var recipientID = event . recipient . id ; var watermark = event . read . watermark ; var sequenceNumber = event . read . seq ; console . log ( "Received message read event for watermark %d and sequence " + "number %d" , watermark , sequenceNumber ) ; }
Message Read Event
 This event is called when a previously-sent message has been read.
Message Read Event This event is called when a previously - sent message has been read .
// All messages before watermark (a timestamp) or sequence have been seen.