Express body-parser Middleware and Express cookie-parser Middleware

Introduction to Third-party Middleware in ExpressJS

In ExpressJS, middleware refers to functions that can be executed in the HTTP request-response cycle. Third-party middleware, as the name suggests, is middleware functions that are not included in the core ExpressJS framework, but are instead developed and maintained by third-party developers.

Third-party middleware can be used to add additional functionality to an ExpressJS application. For example, third-party middleware packages can handle authentication, logging, compression, and more. These packages can be installed using package managers like npm and then included in the ExpressJS application using the app.use() method.

One important thing to keep in mind when using third-party middleware is to make sure that the package is actively maintained and has a large user base to ensure its reliability and security. Additionally, it's important to read the documentation and understand how to properly configure and use the middleware in your application.

Overall, third-party middleware can be a powerful tool to enhance and extend the functionality of an ExpressJS application, but it's important to use them wisely and with caution.

Body-parser

What is Body-parser?

Body-parser is a third-party middleware for processing incoming HTTP requests in Node.js. It is used to extract the request body and expose it on the request object for easier handling.

When a client makes an HTTP request to a server, the request may contain data in the request body, such as form data or JSON data. Body-parser helps to extract this data and make it available in a format that can be easily used by JavaScript code running on the server.

Body-parser supports various types of request bodies including JSON, URL-encoded data, raw text, and even multi-part data. It parses the request body and populates the request object with a body object containing the parsed data.

Body-parser is an important tool for building web applications with Node.js because it simplifies the process of handling incoming data from client requests.

Installation

Body-parser can be installed via npm (Node Package Manager) which comes with Node.js. To install body-parser, follow these steps:

1. Open a terminal or command prompt and navigate to your project directory.

2. Type the following command and press Enter:

3. Wait for npm to download and install the package.

4. Once the installation is complete, you can start using body-parser in your Node.js application.

Example

Here is an example of how to use body-parser in an Express.js application:

Explanation:

Let us now discuss the above code in detail:

• In the above code, after importing all the necessary modules, we are then using the bodyParser.json() middleware function to parse incoming requests with JSON payloads. This middleware function extracts the entire body portion of an incoming request stream and exposes it on req.body.
• We also use the bodyParser.urlencoded() middleware function to parse incoming requests with URL-encoded payloads. This middleware function parses the text as URL-encoded data (which is how browsers tend to send form data from regular forms set to POST) and exposes the resulting object (containing the keys and values) on req.body.
• The extended option allows you to choose between parsing the URL-encoded data with the querystring library (when false) or the qs library (when true).
• We can then define our application logic, such as routes and handlers, in the remaining code block.

This code sets up an Express server that can handle incoming requests with JSON or URL-encoded payloads. The body-parser middleware makes it easy to parse and extract data from these payloads so that it can be used in our application logic.

Errors

Here are some common errors that you may encounter when using a body-parser:

1. body-parser deprecated bodyParser: use individual json/urlencoded middlewares:
   This error occurs when you try to use the bodyParser() function, which has been deprecated. Instead, you should use the individual json() and urlencoded() middleware functions, as shown in the example above.

2. SyntaxError: Unexpected token < in JSON at position 0:
   This error occurs when the body parser is unable to parse the incoming JSON data. It may be caused by invalid JSON data or incorrect use of the json() middleware function. Make sure that the incoming data is valid JSON and that you are using the json() middleware correctly.

3. TypeError: Cannot read property 'x' of undefined:
   This error occurs when you try to access a property of the req.body object that does not exist. It may be caused by an incorrect property name or a failure to properly parse the incoming data. Make sure that the property exists and that you are using the correct syntax to access it.

4. Error: request entity too large:
   This error occurs when the incoming data is larger than the default limit set by the body parser. To fix this, you can increase the limit by passing an options object to the json() or urlencoded() middleware functions, like this:

Cookie-parser

One of the third-party middleware in expressJS is Cookie-parser. Let us discuss it in detail.

What is Cookie-parser?

Cookie-parser is a middleware for handling HTTP cookies in Node.js with Express. It simplifies the process of parsing and setting cookies, which are small pieces of data that are stored on the client side and sent back to the server with each subsequent request.

Cookie-parser provides methods for parsing and setting cookies in a standardized way and also provides additional security features like signing and encrypting cookies to prevent tampering and protect sensitive data.

Installation

To install cookie-parser in your Node.js project, you can use npm, the package manager for Node.js. Here are the steps:

1. Open your terminal or command prompt and navigate to your project directory.

2. Run the following command to install cookie-parser:

   This will download the latest version of cookie-parser and install it in your project directory under the node_modules folder.

3. In your code, you can then require the cookie-parser module and use it as middleware

Helmet

One of the third-party middleware in expressJS is Helmet. Let us discuss it in detail.

What is Helmet?

Helmet is a popular third-party middleware that is compatible with the ExpressJS web application framework for Node.js. Its main purpose is to enhance the security of web applications by establishing various HTTP headers that can prevent common web vulnerabilities, including cross-site scripting (XSS) and clickjacking.

The middleware is built to be user-friendly and easy to configure. It comes with a default setup that includes essential headers such as X-Frame-Options to avoid clickjacking attacks and X-XSS-Protection to activate the browser's integrated XSS protection. Nevertheless, developers can tailor which headers they want to set up and how they are configured through the middleware's customization options.

Employing Helmet can significantly improve the security of web applications with little to no hassle. The middleware's secure defaults and customization options offer a practical approach that saves developers time while protecting against typical security vulnerabilities.

Installation

To install the Helmet middleware in an ExpressJS application, you can follow these steps:

1. Open the command prompt or terminal in the root directory of your ExpressJS project.

2. Use the npm package manager to install the Helmet package by running the following command:

3. Once the package is installed, you can include it in your ExpressJS application by adding the following line of code:

4. To use the Helmet middleware in your application, simply add the following line of code:

   This will enable the default security features provided by Helmet. You can also customize the options by passing an object with specific configuration options as a parameter to the helmet function.

   This will set a content security policy that only allows scripts to be loaded from the same domain and the trusted-cdn.com domain.

By following these steps, you can install and configure the Helmet middleware in your ExpressJS application to improve its security.

Example

Here's an example of how you can use Helmet in an ExpressJS application:

Explanation:

In this example, we are using the helmet to improve the security of web applications by setting various HTTP headers that can prevent common web vulnerabilities such as cross-site scripting (XSS), clickjacking, and more. Here's how it works:

• In this example, we've imported the express and helmet modules and created a new ExpressJS application using the express() function.
• We then enabled the Helmet middleware by calling app.use(helmet()).
• Finally, we set up a simple endpoint for our application using the app.get() function, and started the server by calling app.listen().
• With Helmet enabled, our application will now have improved security by setting various HTTP headers to prevent common web vulnerabilities.

Passport

One of the third-party middleware in expressJS is Passport. Let us discuss it in detail.

What is a Passport?

Passport is a popular authentication middleware for ExpressJS, which is a web application framework for Node.js. It provides a flexible and modular authentication framework that can be easily integrated into ExpressJS applications to handle user authentication and authorization.

Installation

Here are the basic steps to use Passport in an ExpressJS application:

1. Install Passport:
   You can install Passport using npm, by running the command npm install passport.
2. Install a Passport strategy:
   Passport supports various authentication strategies, such as OAuth, local authentication, and OpenID. You need to install a strategy that fits your use case. For example, you can install the local authentication strategy using the command npm install passport-local.
3. Configure Passport:
   You need to configure your Passport by setting up a Passport session, defining a user serialization function, and registering a Passport strategy.
4. Implement Passport authentication:
   You can implement Passport authentication in your ExpressJS application by calling the passport.authenticate() function in the appropriate route or middleware.
5. Handle Passport authentication:
   You need to handle Passport authentication by providing a callback function that will be called after successful or failed authentication.

Example

Here's an example of how you can use Passport in an ExpressJS application with the local authentication strategy:

1. In this example, we've imported the express, passport, and passport-local modules and created a new ExpressJS application using the express() function.
2. Then we have to initialize the passport, by using the passport.initialize() middleware. The passport.initialize() is a middleware, that initializes the passport and sets up the authentication flow. It must be used before any other Passport middleware is used.
3. Then we have setup the passport session, using the passport.session() middleware. This passport.session() middleware is used to support persistent login sessions. It is typically used after passport.initialize(), and must be used before any routes are defined. This middleware is responsible for setting up the session management and serialization/deserialization of user objects.
4. Then we define the passport.serializeUser() and passport.deserializeUser() functions, which are used for user serialization and deserialization, respectively. serializeUser() is called after a user has successfully authenticated and extracts the user ID from the user object, then passes it to the done callback. deserializeUser() is called to retrieve the user information from the session using the user ID stored during serialization.
5. We then registered the local authentication strategy using the passport.use() function. The local strategy's function takes in a username, password, and a callback done. The function then looks up the user in a database, and if the user is found, it verifies the user's password. If the password is valid, the function returns the user object. If not, the function returns false.
6. Then we used the passport.authenticate(), which is a middleware that is used to authenticate the user's credentials against the LocalStrategy. In case of successful authentication, the user is directed to the root path ('/'). In case, if the authentication fails, the user is redirected to the login path ('/login').

Morgan

One of the third-party middleware in expressJS is Morgan. Let us discuss it in detail.

What is Morgan?

In ExpressJS, Morgan is a middleware that is used for logging HTTP requests. It provides a simple and consistent API for logging all incoming requests and outgoing responses.

Morgan works by intercepting incoming requests and outgoing responses and logging information about them, such as the HTTP method, URL, status code, response time, and more. It can log to the console, a file, or any other output stream.

Installation

Here are the basic steps to use Morgan in an ExpressJS application:

• Begin by using the Node Package Manager (npm) to install Morgan into your Node.js project. Open your terminal and execute the following command:

• Once the command has been executed, the latest version of Morgan will be downloaded and installed from the npm registry, while also being added to your project's dependencies in the package.json file.

• Once Morgan has been installed, require it in your code to include it in your project:

• The Morgan middleware will be added to your Express application with the morgan('combined') line of code, which will log HTTP requests and responses in the "combined" format.

Example

Here is an example of how you can use the morgan middleware in ExpressJS to log HTTP requests and responses:

Explanation:

• First, we import the necessary modules: express and morgan.

• Next, we create a new instance of an Express application using express().

• We then set up the morgan middleware using app.use(morgan('tiny')). This tells Express to use the morgan middleware with the tiny format. The tiny format is one of several pre-defined formats in morgan, and it logs the request method, URL, status code, response time, and response size.

• Finally, we start the server by calling app.listen(3000, () => { ... }), which tells Express to listen for incoming HTTP requests on port 3000. The callback function is called when the server starts listening, and it logs a message to the console.

• When the server is running, it will log HTTP requests and responses to the console in the tiny format, which looks something like this:

  This indicates that a GET request was made to the root URL (/), which returned a status code of 200 (OK) and a response size of 13 bytes. The response time is also included in the log output, measured in milliseconds.

CORS

One of the third-party middleware in expressJS is CORS. Let us discuss it in detail.

What is CORS?

CORS, or Cross-Origin Resource Sharing, is a web browser security feature that restricts web pages from making requests to a domain different from the one that served the page. This feature is essential for preventing malicious code from running in the browser and accessing sensitive information.

In an ExpressJS application, you may need to implement CORS if you have client-side code that needs to make requests to your server from a different domain. For instance, if you have a web application operating on http://example.com that needs to request data from your ExpressJS server operating on http://api.example.com, the browser will block the request by default due to the same-origin policy.

To enable requests from different domains, use the cors middleware in your ExpressJS application. This middleware adds the necessary CORS headers to the response, allowing the client to access the response data. The cors middleware allows requests from any domain by default, but you can customize it to accept requests from particular domains by providing options to the middleware function.

Installation

• To add the CORS middleware to your ExpressJS application, use npm, the Node.js package manager. To do this, navigate to your application's root directory in a terminal or command prompt and run the following command:

• This command installs the cors package and adds it to your application's dependencies in the package.json file.

• Next, require the cors middleware in your code and call the app.use() method, passing in the cors() function as an argument. This enables CORS for all routes in your ExpressJS application.

Example

Here is an example of how you can use the CORS middleware in ExpressJS.

Explanation:

• The code begins by requiring the necessary packages, express and cors. After that, an instance of the Express application is created using express().
• To enable CORS for all routes in the application, app.use(cors()) is called. This allows requests from any client that makes a request to the server from a different domain to access the response data.
• A route handler is then defined for the root URL ('/') using app.get('/', (req, res) => { ... }). This HTTP GET request handler sends the response text "Hello, World!".
• Lastly, app.listen(8000, () => { ... }) starts the server on port 8000 and logs a message to the console when the server starts.

The cors middleware automatically adds the appropriate CORS headers to the response when a client requests the server. The middleware allows requests from any domain by default, but it can be configured to allow requests from specific domains by passing options to the middleware function.