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In the last video we set up a subscription inside of our listener and we said that anytime we received

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a message over the channel of ticket colon created we were going to simply counts log.

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Message received.

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If we go back over to our terminal we can select the publisher window and put in our s. a couple of

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times to restart this thing and every single time we do we are publishing a brand new event.

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And clearly the listener is receiving that every single time but right now we're just doing a very simple

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console log of Message received.

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Let's try to print out some more information about the message that was actually received.

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In other words let's actually access the data inside there and try to console log it out back inside

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my listener test file I'm going to take a look at that callback function right there.

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So we receive a argument of message to the thing which we usually abbreviate simply as m as G if we

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hover over that right now typescript thinks that it is of type any we're gonna give typescript a little

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bit of help we're going to tell typescript that this is not a type any.

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Instead it is something of type message to do so we're going to first import the message type from the

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node Nat streaming library.

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So at the very top we will imports message like so this is an interface that's going to describe the

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type of this argument right here.

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So I'm going to put in a type imitation of message like so I'm then going to do a command click on Message

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so we can take a look at the type definition for it so we can understand what properties are available

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inside their that's going to take us to the type definition file for the node Nat streaming library

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that we already looked at one or two videos ago.

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Now just so you know there is documentation around node Nat streaming over on NPM J.S. dot com but a

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lot of the documentation on here is really about some nitty gritty aspects of the library as opposed

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to the individual methods we have access to.

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So to get some actual documentation and understand the different methods properties and so on.

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Do we have access to we're going to spend a lot of time looking at the type definition file so inside

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of here we can see exactly what a message is.

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A message is going to have a couple of different properties associated with it.

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All these are different functions that you and I are going to call to access some information included

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in the message.

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Some of these different methods we don't really care about at all but there are a couple that are extremely

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important for us at this point.

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I want to point out two or three that are really important.

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The first one is get subject right here Get subject is going to return the name of the channel that

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this message just came out of.

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Now this one isn't super important for us because well we already know the name of the channel because

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we just subscribe to it.

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Right.

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Two seconds ago if we called the Get subject method on message we would just get back that right there.

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That same exact string is just the name of the channel that we got the message from.

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So a little bit more relevant for us are the methods of get sequence and get data get sequence is going

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to return the number of this event in that's all events start off at number one.

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In other words the very first event that we emit on a channel will be assigned a sequence number of

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one.

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The second event we met on a channel be given a sequence number of two three four and so on.

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The other method that's very important is get data.

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So this is going to return the actual data.

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That's included inside the message or what we refer to as an event.

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So in our case back inside of our publisher we have some data that we're sending inside of this message

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of some tickets.

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So if we try to pull our data using that get data method out of the message inside of our listener we

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should get back something that looks like this right here.

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Do you remember that all information in that streaming is exchanged as strings for us.

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And so we threw this object in as Jason into that event.

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And so if we tried to extract information back inside of our listener from this message we're gonna

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get that same object.

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But in Jason form which just means we're going to have to run a Jason pass on it and the other thing

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I want to point out is that they get data method is going to return either a string or a buffer.

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So as far as typescript is concerned teacher wants us to make sure that we're actually working with

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the string.

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When we call get data.

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OK.

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So with all this in mind let's go back to our listener inside of our little callback right there.

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I'm going to remove that console log I'm going to pull our data out of the message and so again if we

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now hover over the thing it's going to tell us that it's either a string or a buffer.

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We have to put it a little tight check to make sure we're actually working with the string.

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We're not really going to ever be worrying or dealing with buffers for us.

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It's just about always going to be a string.

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We're just putting in this check right here to make typescript happy they'll say if type of data is

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a string.

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Now let's go ahead and try to pass it and console log out some information.

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So I gonna do a console log I'm going to put a template string inside of here and I'll console log received

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event number and I'm going to try to print out the number of this event or its sequence number so I'll

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do some string interpolation.

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Inside there I'll put in NSG.

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Get sequence

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and then a comma right after let's say with data and then I'll try to pass the data from the Jason that

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it currently is.

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So I'll do a another bit of string interpolation.

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And Jason does pass data I'm going to save this just so it wraps that string around.

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There we go.

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All right.

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So let's make sure we say this.

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We're then going to go back over to a terminal and tested out so as soon as our listener restarts.

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Well we have not yet received an event if we want to test this thing.

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We need to publish another event.

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So we'll go back over the publisher window but in the RSS hit enter and now we'll see right there received

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event 18 with data.

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And unfortunately our data was turned into object object just an oddity of console logging with no J.S.

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rather than passing the Jason out.

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Let's just leave it as a string so we can make sure that the raw data is inside there.

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So back at this console log I will remove the Jason pass and just console log the data itself I'll say

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this go back over I'm going to emit another event by doing another R S on the left.

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And that's better.

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So now I see it received event number 19 with that data.

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If I start to publish a couple more events by restarting at the publisher you're going to see that that

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sequence number gets incremented every single time so event number 19 20 21 22 23 and so on.

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Go.

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All right.

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So just a little bit more of terminology and how we work with the incoming message.

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I did promise at the end of last video that things were about to get all that crazy doesn't seem like

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it yet.

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Right.

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Okay well just give me another video or two so quick pause.

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I'll see you in just a minute.