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Published: 2024-01-21 18:34:22

introduce to me these codes line by line with easy example in real world = 
const MongoStore = require('connect-mongo')(session);

        app.use(session({
            secret : 'mysecretkey',
            resave : true, 
            saveUninitialized : true, 
            store : new MongoStore({ mongooseConnection : mongoose.connection })
        }))

Sure, I can try to explain these codes with an easy example in the real world. Imagine you are visiting a website that requires you to log in with your username and password. When you do that, the website creates a **session** for you, which is a way of keeping track of who you are and what you do on the website. The session is stored on the website's server, but it also sends you a small piece of data called a **cookie**, which contains a unique **session ID**. The cookie is stored in your browser and sent back to the website every time you make a request. This way, the website can identify you and show you personalized content based on your session.

Now, let's see how these codes relate to this example:

```javascript
// This line imports the connect-mongo module and passes it the session module as an argument.
// The connect-mongo module is a tool that helps the website store sessions in a MongoDB database, which is a type of database that stores data in documents.
// The session module is a tool that helps the website create and manage sessions and cookies.
const MongoStore = require('connect-mongo')(session);

// This line uses the app.use() method to register a middleware function that handles sessions.
// A middleware function is a function that runs before the website responds to a request, and can modify the request or the response.
// The session() function takes an options object as an argument and returns a middleware function.
app.use(session({
    // This option sets the secret key that is used to sign the session ID cookie.
    // The secret key is a random string that is not easily guessed, and it is used to make sure that the cookie is not tampered with by anyone else.
    // For example, the secret key could be 'mysecretkey', and the session ID could be '1234567890'. The website would use the secret key and the session ID to create a signature, such as 'abcdefg', and append it to the cookie, such as '1234567890.abcdefg'. This way, the website can verify that the cookie is valid and not forged by someone else.
    secret : 'mysecretkey',
    // This option controls whether the session should be saved to the store even if it was not modified.
    // For example, if you visit the website and do nothing else, your session would not be modified. But the website might still want to save your session to the database, so that it can keep track of how long you have been inactive, and delete your session after a certain time. This option would be set to true in that case.
    resave : true, 
    // This option controls whether a session should be created for requests that do not have one.
    // For example, if you visit the website for the first time, you would not have a cookie or a session. But the website might still want to create a session for you, so that it can store some information about you, such as your preferences or your shopping cart. This option would be set to true in that case.
    saveUninitialized : true, 
    // This option sets the store where the sessions are stored.
    // Here, a new instance of the MongoStore class is created and passed the mongoose connection object.
    // The MongoStore class is a tool that helps the website store sessions in a MongoDB database, using the mongoose connection object, which is a tool that helps the website connect to and interact with the database.
    // For example, the website might store your session in a document like this:

    // {
    //   "_id": "1234567890.abcdefg", // the session ID and the signature
    //   "session": {
    //     "username": "john", // your username
    //     "cart": ["apple", "banana"], // your shopping cart
    //     "expires": "2024-01-22T22:00:00.000Z" // when your session expires
    //   }
    // }

    store : new MongoStore({ mongooseConnection : mongoose.connection })
}))
```

I hope this example helps you understand the codes better. If you have any more questions, feel free to ask me. 😊.