Introduction to JavaScript and its industrial use cases.

JavaScript

What is JavaScript ?

JavaScript is a dynamic computer programming language. It is lightweight and most commonly used as a part of web pages, whose implementations allow client-side script to interact with the user and make dynamic pages. It is an interpreted programming language with object-oriented capabilities.

JavaScript was first known as LiveScript, but Netscape changed its name to JavaScript, possibly because of the excitement being generated by Java. JavaScript made its first appearance in Netscape 2.0 in 1995 with the name LiveScript. The general-purpose core of the language has been embedded in Netscape, Internet Explorer, and other web browsers.

Client-Side JavaScript

Client-side JavaScript is the most common form of the language. The script should be included in or referenced by an HTML document for the code to be interpreted by the browser.

It means that a web page need not be a static HTML, but can include programs that interact with the user, control the browser, and dynamically create HTML content.

The JavaScript client-side mechanism provides many advantages over traditional CGI server-side scripts. For example, you might use JavaScript to check if the user has entered a valid e-mail address in a form field.

The JavaScript code is executed when the user submits the form, and only if all the entries are valid, they would be submitted to the Web Server.

JavaScript can be used to trap user-initiated events such as button clicks, link navigation, and other actions that the user initiates explicitly or implicitly.

Advantages of JavaScript

The merits of using JavaScript are −

• Less server interaction − You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.
• Immediate feedback to the visitors − They don’t have to wait for a page reload to see if they have forgotten to enter something.
• Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.
• Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.

Netflix and node.JS

Netflix is a streaming service that offers a wide variety of award-winning TV shows, movies, anime, documentaries and more — on thousands of internet-connected devices.

You can watch as much as you want, whenever you want, without a single ad — all for one low monthly price. There’s always something new to discover, and new TV shows and movies are added every week!

Netflix is now among companies using Node.JS due to the following reasons:

• A common language both for the server-side and browser side.
• High performance — now the page loads within seconds.
• A great number of modules and their open-source nature.
• An easy way of writing, debugging and engineering the API.

Netflix initially used Node.js to enable high-volume web streaming to over 182 million subscribers. Their three goals with this early infrastructure were to provide observability (metrics), debuggability (diagnostic tools), and availability (service registration). The result was the NodeQuark infrastructure. An application gateway authenticates and routes requests to the NodeQuark service, which then communicates with APIs and formats responses that are sent back to the client. With NodeQuark, Netflix also created a managed experience — teams could create custom API experiences for specific devices. This allows the Netflix app to run seamlessly on different devices.

Beyond streaming

However, Netflix wanted to move beyond web streaming and into content production. This posed several challenges to the NodeQuark infrastructure and the development team. Web streaming requires relatively few applications but serves a huge user base. On the other hand, a content production platform houses a large number of applications that serve a limited userbase. Furthermore, a content production app must have multiple levels of security for employees, partners, and users. An additional issue is that development for content production is ideally fast-paced while platform releases are slow, iterative processes intended to ensure application stability. Grouping these two processes together seems difficult, but the alternative is to spend unnecessary time and effort building a completely separate infrastructure.

Hermeto decided that in order to solve Netflix’s problems, he would need to use self-contained modules. In other words, plugins! By transitioning to plugins, the Netflix team was able to separate the infrastructure’s functions while still retaining the ability to reuse code shared between web streaming and content production. Hermeto then took plugin architecture to the next step by creating application profiles. The application profile is simply a list of plugins required by an application. The profile reads in these specific plugins and then exports a loaded array. Therefore, the risk of a plugin built for content production breaking the streaming application was reduced. Additionally, by sectioning code out into smaller pieces, the Netflix team was able to remove moving parts from the core system, improving stability.