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So we played around with Node.js a bit and we saw one of its built-in core modules which you can pull in to

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add certain functionalities which are not available in the browser but which are available in Node.js.

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One important difference compared to the browser of course is that some modules need to be imported

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with this syntax in order to use them whilst others are available globally and most modules actually

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need to be imported by the way, in the browser

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all the things by default are available globally,

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you can just access documents like this,

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you can just access local storage like this.

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That's one difference, in Node.js, 

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it's more of you have to tell me what you need approach, other than that

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however, it's highly comparable,

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we have the same base language and then some specific APIs.

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Now let's move away from this dummy script here,

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I'll name it files.js and add a new app.js which is empty and let's see what we can do in Node.js

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when it comes to working with HttpRequests because that arguably is an important scenario where you

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would look to Node.js running a web server with it.

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So let's see how that would work.

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It all starts with a specific module

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you can require and that's the HTTP module,

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it's a module that allows you to work with HttpRequests This by the way does not just mean that you

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can listen to them,

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you can also create a request and send it to a server but more commonly, you use Node.js to set up a

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server that listens to incoming requests so that you can have your own web server and in the end by

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the way, that's also what the webpack

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dev server and all these other development servers do, they use Node.js to set up a basic web server

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which runs locally on your system to host your HTML files, your simple local web application.

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Now we'll basically do the same here but we'll not just build our own development server but instead

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we'll build a server which also runs some server-side logic, something

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development servers of course don't do, they just serve our local files. Now to get started with that,

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we need to create a server and for that on the HTTP method,

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we can call create server. The create server method does just what it sounds like and it requires one important

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argument for that,

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a request listener,

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this is a function which in the end triggers for every incoming request.

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This request listener function takes two arguments which are passed in automatically by Node.js and

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that's a request object and a response object.

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So this will basically be passed in by Node.js and will reflect the request which was coming in, so

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the headers which are part of the request, the data which might be part of the request and so on and this

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response object is also given to you by Node.js, it's an object which you can then use to configure

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the response you want to send back and to then ultimately send it back.

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So inside here of

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create server, we can now work with these two pieces to read data from the incoming request and to send

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back a response and to start

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very simple, let's start with the response object to right now do nothing with the incoming request but

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to just send back a response and there we can call write, to write some data to the response,

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for example a simple string where we say hello there and then we can call end which will send the response,

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so end basically tells Node.js we're done adding data to the response,

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you can now close it and send it back

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and this is a very simple web server

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we could build with Node.js.

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Now with the server created, we need to do one more thing though, we need to call listen on it,

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so we either chain this here or we take the extra step of storing this in a separate constant and then

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we call listen on this constant, so on the object, on the server object stored in the constant. Listen is

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required to then actually start the server,

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you can think of create server as a method to build the server but then listen starts it up and listens

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to incoming requests.

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Listen also takes the port on which you want to listen

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and here I'll go for 3000 for my local development only to use this special port locally here.

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With that if we now save this, we can again run our app.js file which now holds the server and you

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will notice something interesting. If I do that, we don't get an error

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but we also don't complete this process, my cursor here in the terminal is stuck.

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Now you can always quit this by hitting control c but it is stuck for a good reason, it is stuck because

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this is an ongoing process,

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this script now doesn't finish

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once all the lines have been parsed, instead listen in the end sets up an ongoing event listener you could

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say behind the scenes which waits for incoming requests

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and as long as Node.js notices ongoing event listeners, it does not shut down script execution which

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is why this script execution is still going on, because we have ongoing event listeners and that's of

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course what you want,

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you want your server to keep on running and not to quit after it was configured, right?

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So now we get this ongoing server and to see it in action,

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all we have to do is we have to visit localhost:3000 and there, you should see hello

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there on this page. You see hello there there because that's of course the data we are sending

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back in the simple response.

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It's not HTML data or anything like that,

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IT's a simple text but we see it here on our own

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Node.js server and now we're back in the browser

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but this is now not browser side Javascript,

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in the end this is the result of server side Javascript which spins up a server and sends back a response.