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So in this basic script here, just output something in the console.

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Now how about writing this data to a file and then reading the data in from a file?

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For that, we need a couple of packages which are available when you install Node.js. Node.js works such

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that certain, very important features are available globally, for example setTimeout.

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This is a browser API that was also implemented in Node.js and you can just use it like this in

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any Node.js file but other functionalities which you don't need that often need to be imported explicitly,

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for example functionalities for working with the filesystem, for that Node.js works with so-called

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modules and on nodejs.org, you can learn more about that. In the docs there,

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if you click on API reference, you'll find all the packages, all the core modules Node.js is made up

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of and

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for example here under f you find the filesystem module and you find the complete documentation for this

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module.

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Now as you can tell, there's a lot in there and of course we'll just briefly dive into this but we will

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use it a bit at least.

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So there for example we see how we can make this module and its features available in a Node.js script

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and that's one important difference to browser side scripts,

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the Node.js import export syntax looks a bit different,

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instead of using the import and export keywords, in Node.js you use require to require a module, be

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that a module provided by Node.js

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like in this example or be that your own file and then you store the required data in your own constant

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which you can then use in your script and I will later also show you how you export something.

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So with that, let's copy that and add this here in our app.js file and this pulls in the filesystem module

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which again was already installed as part of Node.js, so we don't need to install it separately but

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we still need to add it to this file with this line and now we can use the filesystem object here to

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work with the filesystem, for example to call the write file method here which takes a path to a file

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and then the data we want to write to that file and there we could, as a simple starting point, just provide

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a file name and then this will be written in the same path as the script sits in,

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for example we could write this to user-data.txt let's say, to write a text file and then

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as a data, we could have some text here,

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user name equals Max for example. You can also defined some write options here as a third argument where

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you can set things like the encoding and so on but we don't need this here, we can just execute this

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file like this.

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Now write file then takes a callback as a third argument which potentially holds an error if it failed

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and we can then check if we do have an error, in which case we could console log it for example and otherwise

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we know we succeeded and we could console log wrote to file and now with that if we now execute our app.js

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file, you see wrote to file here and you should have a new file being added here to your system

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where our data was written to and this is how easy you can write a file with Node.js.

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Of course you can also read in a file, so parse a file, you do this with the filesystem here with read

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file and then the path to the file, for example with user-data.txt,

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then again you can set some arguments or just provide your callback here,

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this is a callback function that takes two arguments, first argument is a potential error object which

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will be undefined if we have no error,

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second argument is the data we hopefully get and then here we can check if we do have an error and if

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we do have one, we can console log the error and then maybe return to not continue with the execution

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and otherwise, we'll get our data.

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So let's see what we get there if we print this

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and now if we save that and we run this script again, we see wrote to file but we also see this buffer

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output here which is coming from parsing the file.

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Now of course that buffer is not that useful, if we call to string on that, it gets more useful though,

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now this is converted to a string and we got the content of the file being output there.

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So this is a very simple Node.js application of course if you want to call it like this but we see

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some Node.js APIs in action here and at the same time we see regular Javascript syntax, like the

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if statement which we use here or the const keyword which you of course learned about throughout this

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course.