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Welcome to your very first programming video for the class.

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From here on out we're going to be spending our time writing code and building note applications in

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Visual Studio code.

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Now in this video in particular to kick off the course we're going to talk about one of the most fundamental

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features of node.

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This is the module system and this is what's going to allow us to take advantage of all of the cool

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and interesting things that node provides.

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So as an example over here in the docs there are all sorts of modules listed.

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Now some as we saw with console are available globally which means we don't have to do anything special

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to use them right here as an example.

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We just accessed console dot log to use it.

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Others require us to actually load them in before they can be used in our scripts.

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That's exactly what we're going to explore.

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And the module we're going to use to explore this is the file system module listed down below.

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This is the module that's going to allow us to access the operating systems file system.

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We'll be able to read and write append files and figure out if a given file or directory exists.

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All sorts of interesting utilities related to the file system at the table of contents here contains

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all of the interesting ways we can use this module inside of our node applications.

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And if we start to scroll down we can see there are quite literally hundreds of different ways.

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Now at some point we're going to get to a part in the Table of Contents where everything starts with

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F. s dot followed by some method name here as an example I have f s dot access all these methods are

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listed in alphabetical order and we're going to scroll down to the method we'll be using which is F

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S dot right file.

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This is the method that's going to allow us to write some data to a file on our file system from the

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node j s application.

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Now we have two versions of this I have f s dot right file and F S dot right file sync.

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The first one is an asynchronous version and the second one is a synchronous version.

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And for the moment we're going to stick with the synchronous version.

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Don't worry though we will be exploring asynchronous know j s in detail in just a couple of sections.

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For now though the goal is to learn about this module system so F Scott right file sync takes into arguments

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the name of the file you want to write to and the data you want to write.

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So let's go ahead and use it.

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I'm gonna head over to the Visual Studio code editor and I will take a moment to delete Hello Dot J

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S as this is not gonna make it into any of our applications.

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Let's go ahead and trash it and we'll make a brand new folder for our first project which is going to

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be a little notes app so I'll call the folder Notes app and in there we're going to make a single j

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ust file right here app dot J.

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S now down below inside of the terminal.

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I am going to switch directories from node course to Notes app by using d space.

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Then the folder name notes hyphen app.

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Now we're actually running commands from that directory and that's great because we're going to run

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node in just a few seconds.

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Let's go ahead and actually use F S dot right file sync exactly like we saw in the docs it is F S which

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is an object dot the method name is right.

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File sync it is indeed a function.

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So I am going to call it as such.

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Setting up my parentheses and as I mentioned this takes two arguments in this case both are strings.

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The first is the name of the file.

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The second is the data.

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All right let's go ahead and pick a name for our file and I'm going to call this something like notes

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Dot T X T.

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So for the moment we're going to stick with a simple text file though later on we'll learn how to work

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with files of other types.

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Now the second argument is going to be the contents to put in that file.

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So right here as a string let's go ahead and write out a little message.

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This file was created by node j s perfect.

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So now we actually have a call to write file sync and we can go ahead and run this script.

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The problem is that it's not going to work down below.

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Let's prove that I'm going to use node to run a script after a space the script name is app dot J S

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which is indeed in the directory we're running commands from the notes app directory.

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If I go ahead and hit enter we are not going to see any sort of output that suggests that things went

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well.

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Right here we have a very long error message.

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It contains information about exactly where the error occurred and what exactly is going wrong.

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Now later in the course when we explored debugging we'll really break down errors like this for the

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moment.

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The only important piece is this little message right here F S is not defined.

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So the problem is that we're using F S F S though needs to be loaded in and define the file system module.

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As I mentioned has to be required by you in the script you're using it in.

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So right here we're gonna add a second line before we use the file system module.

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We're gonna go ahead and load it in and this is done using the require function that node provides.

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And this is at the very core of the module system.

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The require function is how we load in other things whether it's a core node module a another file we

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created or an NPM module we've chosen to install into use in our projects to load in the file system

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module we have to call the require function which is indeed how we load in modules and we pass to it

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a single string.

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Now when we're looking to load in a core node module we just provide the name of the module and for

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the file system it is f s.

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Now they require function returns all of the stuff from that module and we have to store that on a variable

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right now f s still doesn't exist.

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So right here we're going to create a constant called F S and it's value is going to come from the return

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value of calling require.

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So let's break this down.

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We're calling require which is going to load in the F S module the FSA module is built right into node.

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So this is going to work for any node script.

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What do we do with the return value we store it on the F S variable then down below we call f s dot

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right file sync to write some text to the notes Dot T X T file.

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Let's go ahead and see if this works down below.

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I'm gonna start by clearing the terminal output using the clear command.

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If you're on Windows and you're using these standard command prompt you're gonna have to use S.L. s

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which is the command for you.

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And now we're gonna go ahead and run the app script again.

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So node space app that J.

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S this time what do we see.

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We see nothing it brings us right back to the command prompt asking us to do something else but you'll

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notice that over here in the preview for the notes app directory we have a brand new file right alongside

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of app dot J S we have notes Dot T X T which got its name from this argument.

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And if I crack it open what do we have.

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We have our little message in this file was created with node j s which is fantastic.

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Now let's go ahead and switch up the text where writing and run the script again.

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So over here I'm gonna change the text value for that second argument and go ahead and do the same.

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I'll switch it up to something like an introduction.

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I'll say my name is Andrew.

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Period.

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Perfect.

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Now we can rerun the script to write some new contents to that file down below.

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I'm gonna use the up arrow key to cycle through my previous commands here.

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The previous one we ran was node running app at J S then I'll hit enter to run the script again once

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again nothing output it down below.

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But if I open up notes Dot T X T we have our new text content showing up which is great.

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So the right file and the right file sync methods those are responsible for writing data to a file.

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If the file doesn't exist as we saw it will be created if the file does exist as we just saw its text

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content will be overwritten with the new provided message.

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I want to take a quick moment to note that this variable F S it could be called anything we wanted.

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The only important thing is that the string we passed to require matches up with what node calls the

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module.

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Otherwise node is not going to know which module you're trying to load.

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So as an example I could call this something like a file system and that would be perfectly valid as

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long as I changed my usage down below to file system as well.

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Now we have a different name for the variable and the program would work though it's common to stick

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with the convention for all node modules we load in there's typically a variable name that everyone

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uses and it makes life easier if we all stick with that variable name so we can know what exactly we're

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working with across projects.

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Now if you're wondering how I knew to load an F S or what the common variable name is or whether the

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module even needs to be loaded in at all.

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Once again the docs are your best friend.

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If we go back over to the documentation and scroll down past the table of contents one of the first

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things we're going to see is what we have on line one.

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Here we can see exactly what node calls the module based off of the fact that this code is here.

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We know it needs to be loaded in unlike console and then they have a common used a variable name which

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we can choose to use or choose to ignore.

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Though once again it is a best practice to use the name in this case f S..

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So at this point we have loaded in our first core node module and we've used it to do something interesting.

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Now I want to take a moment to move on to our first challenge for the class.

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Whenever I write code in a video you should be following along as well.

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I film all of the videos in real time so you can actually write the code I'm writing.

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That is a great way to learn something but it's not the best way to make sure you can actually use that

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information to solve problems.

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So throughout the course in almost every single video I have a challenge where you're going to need

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to solve a programming problem based off of what you just learned.

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The goal here is to give you as much real world experience as possible actually using node j s on your

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own by the end of the course.

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You'll actually have a ton of experience writing your own code and building your own apps and you'll

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find it much more comfortable to go off after the class and actually use no J.S. whether you're building

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your own side project trying to get into freelancing or trying to switch careers and become a node j

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ask developer.

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So it's important that you follow along with the lessons.

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For example you should have this code in your editor.

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It's also equally important that you take the challenges seriously.

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So here's how they work.

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I give you a prompt I give you a second to pause the video.

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You go off and solve the problem.

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Then you come back and I walk you through the solution.

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So let's go ahead and jump into our very first one as always.

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I'm going to paste in a little description of what I'd like you to do.

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So this is a pretty standard challenge.

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Now they're gonna start off easy and they're going to get harder over time as we actually know more

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about node and we can do more things right here challenge.

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Your goal is to append a message to notes Dot T X T.

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So I don't want to override what's here.

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I want to add something new on it to the end.

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How are you going to do that.

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You're going to use a new method from the file system module called append file sync to append to the

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file.

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Once you've added that in you're going to run the script.

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And finally you're going to check your work making sure that the new text you append is showing up on

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the end right here.

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Now to do that we are going to comment out our existing F S dot in a right file sync call.

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We're going to add just that one call in the call to append a file sync and if we head over to the documentation

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you can learn more about that.

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I'm going to scroll up back to all of those modules and methods we were looking at earlier and if I

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go all the way up to F S Dot and I go to the A's I have append file sync right here.

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Now append file sync works much the same way as right file sync it needs the name of the file you're

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trying to append and it needs the text content you want to append so in the end of the day we want to

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append to the file whose name is right here and you can pick whatever message you want as the text to

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append.

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You could add to the introduction saying something maybe about where you live or how old you are.

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If the concept of a challenge it seems a little foreign to you.

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Don't worry we're gonna go through this about a hundred different times throughout the course.

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So you'll be pretty comfortable with it by the end and as I mentioned things are gonna start off easier

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as we know less about node and the challenges will get more complex requiring you to write many lines

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of code.

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As we progressed through the class for now though it takes some time to knock out all three steps down

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below.

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You can pause the video when you're done come back and click play

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how'd that go.

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Very first challenge down.

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Hopefully it went well.

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If it didn't.

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That's OK too.

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This is really an introduction to challenges and once again we'll get more comfortable as we do more

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of them right here.

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The goal was to use f data append file sync.

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Now this is already a module we have loaded in so there's no need to load it in again.

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Right here we can call f s dot append file and you'll notice that since we've loaded in the FSM module

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with visual studio code at least I am getting some helpful suggestions about which methods I have access

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to.

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Right here I will be using append file sync and calling it as such.

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Now what file am I trying to append to.

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Well I only have one it is notes dot t t so that will be the value I provide for the first argument

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and for the second argument I'm gonna provide the text I want to append I'll say something like I live

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in Philadelphia.

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Perfect.

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Now since we're appending one string right on to the end of the other I'm gonna put a space at the beginning

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of the string.

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So I have a space between the period up here and the letter I down below.

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Now we can go ahead and save app not J S and run our script to test things out.

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I'll use the up arrow key and enter to rerun the previous command and if I open up notes dot t t what

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do we have.

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I have my old message My name is Andrew and I have my new message.

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I live in Philadelphia which is excellent.

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And there we go.

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You've completed your very first challenge.

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Once again these are essential to getting real world experience solving problems and working through

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your misunderstandings so it's okay if you don't get them all right or it takes you a lot of time to

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figure out what's going on.

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It's gonna get easier to recall what we covered as we use it more and more now that we're starting to

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write code together.

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I wanted to remind you that the lecture resources for every lesson of the class contains a zip of the

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code up to that point.

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So if you're getting stuck and you can't quite figure it out you can always download the zip for that

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lesson that contains all of the code changes made and you can compare your code with my code.

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You can also head over to links.

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Dot need dot I O forward slash node course to view a get Hub Repository that contains every piece of

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code created in the class.

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That's where we're gonna stop for this one we've now loaded in and used our very first core no J.S.

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module in the next video we're gonna continue to talk about the module system and require.

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I am excited to get to that.

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So let's go ahead and jump right in.