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So let's connect to mongodb

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and for that, make sure you are on your clusters page so that you can click on connect there and find out

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how to connect to this cluster.

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Now we did connect through the shell in the past,

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now we can also connect our application and for that, yes we are using the latest driver

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and then you can just copy that address if you want.

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You can also see the driver examples if you click on it down there,

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so if you click on node here, you're basically forwarded to some part of the Atlas documentation in this

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case where you see a code snippet on how you can connect to your address and you'll have to replace

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some data there through the official driver

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but we'll do this step by step.

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So let's go back to the cluster,

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copy that here and then head over to your code and in there,

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let's start in the app.js file,

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this is the file where basically all requests end up in which are sent to your node backend.

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So whenever the frontend react sends some requests to the backend like get me all products,

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first of all we start in this file, then in node express, the request is basically funneled through some

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middleware as it's called,

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so some functions that can interact on the incoming requests like set some headers here and then here,

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I forward the requests to different routes, so different handlers you could say depending on whether I'm

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requesting something related to products or just /nothing.

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The routes are stored in the routes folder and for products in here, I have some dummy data but there, I have

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a route for get requests

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if it's just sent to /products, I just have slash here because the products filter is in the app.js file,

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so if it's targeting /products, then this function is executed essentially and there, what I do is

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I have some pagination logic in there which we can ignore for now,

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I basically parse my dummy data and I return my data here,

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so this is what I'm doing here. Now

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app.js is also the file where the code is executed

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when we start up our server, which we did with this npm run start server command. This basically just

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use

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nodejs,

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basically we executed this script where we used nodejs to execute the app.js file and the app.js file

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does some general setup like setting up all that middleware which will handle incoming requests and

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therefore, we can connect to mongodb here in this file to automatically connect our app to the database

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whenever we start the app server and we want to have a running connection so to say which can then do something

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for incoming requests right from the start.

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So here, the first thing we have to do is we have to import our mongo client, for this I'll create a new

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constant,

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so a new value which you will never change and then this is the import syntax in nodejs

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and I will require mongodb, that is the package name of the package we installed

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and there, the mongo client,

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so this gives us access to the client which we need to establish a connection and so on. And what we can do now

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at any point you want, maybe down there, you can use that mongodb constant and call connect

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and this is also what you saw in that snippet

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here. There you also see that constant or variable here was just named differently

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but then I called connect and to connect, you pass that connection url and then you have a function

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which is executed after the connection completed.

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So here we can paste in that connection url which we got from the cluster page. Now important, you

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will need a user name and for that user, you will also need a password,

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so I'll just use that one, by the time you're viewing that, this will be offline

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so using mine won't make much sense, then I'll use the Maximillian user, so I'll use that read and write

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user here

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and for this user, I just updated the user, the password and I'll paste the password in here too.

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So now this is a url which allows the client to connect to the cluster,

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I don't want to use the test database but I'll use a shop database which will be created on the fly

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and with that, the connection will be established and now we could pass a function as a second argument

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which will be executed when the connection finished or we use a feature called promises where we basically

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have a then method to which we pass a function that will be executed once this connection finished

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or we have a catch block that catches any potential errors.

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Now here in the catch block, I'll simply output the error so that we can see it,

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console log basically basically logs it to this console

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so that we could see error messages here

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and in then, I basically have an anonymous function and this is just how you create an anonymous function

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in javascript that will execute

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once we are connected.

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So here I can say connected and here as an argument, I will actually get access to the client, so a client

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which then allows me to execute a database method which then in turn allows me to for example work

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with collections and so on.

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So we'll do this later,

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for now we can instantly close the client to remove the connection,

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we'll of course later reuse it

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but for now I'll immediately close it and just log connected in-between. Now after saving this and

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after changing your server side code, you have to go to the terminal where you ran npm start server

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and quit that process with control C and simply restart it because you changed something in your application,

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now you need to restart it and after restarting, you should be able to connect to your mongodb database

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server to the Atlas cluster.

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Now with being connected, we took a first step but of course we're not doing anything useful here,

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so in the next lectures, we'll of course start writing some code so that for example when we add new

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products here, we store them in the database. That sounds like a good start so that we later are also

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able to fetch them, doesn't it?