The MEAN architecture is comprised of four different JavaScript technologies when they are stacked successively. The architecture is designed so that each component performs specific tasks individually as well as in sync with other layers in the stack to achieve an end goal.

In the MEAN architecture that's shown in the following diagram, the client initiates the requests, which flow right from the first layer down to the last. Appropriate responses to those requests then flow right through all the layers back up to the client.

The client first interacts with the user interface, which is built using the Angular frontend framework. Requests made on the interface are passed to Node.js, the server-side engine. Then, the middleware framework known as Express.js makes a request to MongoDB, which is the database. Express.js retrieves the response in the form of data from the database. Finally, this response is then returned by Node.js to the client via the user display:

Figure 1.2: Workings of the MEAN architecture

There are several advantages to using the various MEAN components, which has made it a technology stack to reckon with for start-ups and big companies alike. There are several reasons why the MEAN stack is preferred in web application development. A few of these reasons are listed here:

Owing to its performance benefits, the MEAN stack has been adopted by many contemporary commercial organizations, such as Uber, PayPal, Netflix, and so on to build their websites and web applications. Ulbora and Trakit.me are a couple of other web applications that are built using the MEAN stack.

Before going into MEAN application development, we will briefly discuss the individual technologies that make up the MEAN stack. We will start with MongoDB.

MongoDB

MongoDB is a document-oriented database program. The database, which is classified as NoSQL, is developed by MongoDB Inc. It's a free and open source database that uses JSON-like documents with schemas. Described here are some of the major features that make MongoDB stand out in application development:

Strong consistency: Strong consistency is a default feature in MongoDB, and thus it takes no additional upgrades to create consistency. It's also highly guaranteed: as long as a write is successful, you will be able to read it. Automatic failover of the replica set makes it highly available. Also, flexibility and scalability are not readily available in traditional databases that only rely on a defined schema. In comparison, MongoDB, which is NoSQL, relies on the key-to-value pair approach. This enables flexibility and scalability in MongoDB.

Real-time aggregation: This is a built-in MongoDB feature that allows real-time statistical analysis and the generation of pre-aggregated reports on request.

Ad hoc queries: These are impromptu queries that are written to extract information from the database, but only when necessary.

Indexing: Indexing in MongoDB makes it easy to search documents without performing a collection-wide scan by matching specific queries with documents.

Database-as-a-service: Database-as-a-service offerings by MongoDB enable users to access databases without having to install software or set up hardware. MongoDB Atlas, which is a cloud-hosted service offering by MongoDB Inc., will be used in this book. As we progress in the next chapter, we will go through all the processes involved in its setup.

Despite having several advantages, there are a few limitations of MongoDB that we need to be aware of:

Limited data size: Documents have a maximum data size of 16 MB.

Limited nesting: The maximum number of documents that can be nested is 100.

Joins not supported: This is one of the main differences between RDBMS and NoSQL. MongoDB is not designed to have related columns. Rather, it stores de-normalized data and thus joins are not supported.

However, these limitations cannot overshadow the fact that MongoDB provides high performance, high availability, and automatic scaling, thus mitigating—if not completely eliminating—the preceding limitations.

So far, we have introduced the MEAN stack and its database component, MongoDB. We will now continue with the introduction of the second component, Express.js—a middleware application framework for developing web applications.

Express.js or simply Express is a Node.js web application framework that provides a strong set of features for web and mobile applications. It's free, open source, fast, un-opinionated (that is, there is no "right way" to complete a certain task in Express), and is comprised of a simple web framework that's designed for building web applications and APIs. The framework has achieved a dominant position in the industry as the server framework for Node.js. Express possesses rich features and advantages. A few of these are listed as follows:

The preceding list includes a few of the most dominant features and advantages of Express, and each of them contribute to the performance benefits afforded by this framework. In Express, third-party plugins (middleware) can be set up to respond to HTTP/RESTful requests, and a routing table can also be defined to perform different HTTP operations. HTML pages are dynamically rendered by Express based on passing arguments to templates. Express supports a wide range of templating languages, such as Pug, React, hbs, and h4e. Furthermore, it has detailed documentation to help developers maximize its uses. The community support is huge: as of now, Express has gathered over 30,000 GitHub stars, which means that it is well accepted and supported in the open source community. Also, Express allows for the addition of custom code. In terms of performance, Express leads other frameworks because of its inherent properties that make the routing process efficient and faster.

Express presents a thin layer that enables the addition of robust features and functionalities to your web applications. It organizes web applications into a model view controller (MVC) architecture and manages everything from routes, to rendering views, and pre-forming HTTP requests.

However, we do need to be aware of certain limitations while developing apps in Express. In a real-life situation, when projects become more complex and code base size increases, refactoring becomes very complex and a lot of manual labor is required. This is because the absence of organization makes the handling of complex applications difficult as Express is not designed to manage complexity by itself. Furthermore, the cost of scaling increases with application complexity.

In this section, we introduced another MEAN stack component – Express.js. We described its features and viewed popular Node.js frameworks that have been built using Express.js. In the next section, we will continue with the introduction of the third component, Angular.

The next component after Express in the MEAN stack is a JavaScript frontend framework known as Angular. We will be introducing Angular features across all of its existing versions, and then we will talk briefly about its advantages and limitations.

Angular is an open source TypeScript and JavaScript-based frontend web application structural framework and is managed and sustained by Google. Being open source, a community of software developers and corporations provide maintenance and address issues that are encountered when developing single-page applications. Listed here are some of the advantages that make Angular stand out:

However, note that no framework is perfect and there have been several Angular versions. The following list shows how Angular has evolved over the years, along with its different versions:

However, you should be aware that no web framework is perfect, and in the case of Angular, its verbosity and complexity renders it a difficult framework to master. Furthermore, Angular has a steep learning curve.

In this section, we introduced the third component of the MEAN stack – Angular. We discussed its features, as well as its limitations. In the next section, we will introduce our final MEAN component, a server-side technology known as Node.js.

Node is an open source program that is built on a JavaScript runtime engine (Chrome's V8) and consists of JavaScript libraries that are implemented in the form of modules. The cross-platform server environment is lightweight and efficient because it uses an event-driven, non-blocking I/O model. For example, PayPal employs Node to solve the problem that arises owing to the boundary between the browser (client side) and server (server side) by enabling both to be written in JavaScript. This, in turn, helps PayPal unify their engineering specialties into one team, thus enabling them to focus on user needs and create solutions to meet these on the technology stack level. Some other websites and applications built on Node are eBay, GoDaddy, Groupon, Uber, Netflix, Mozilla, Yahoo, LinkedIn, and so on. The outstanding performance offered by Node makes it the heart of the MEAN stack. According to a number of benchmarks, JavaScript technology for the backend outperforms several other backend programming languages, such as PHP, Python, and Ruby. Listed here are some of the major advantages of Node:

However, you should be aware of a few points before beginning application development in Node. Using relational databases in conjunction with Node might be a daunting task because Node does not provide support for them. Also, using Node is unsuitable for heavy-computation applications. Having given an overview of Node, we will now progress and build our first Node application in the next section.