Chapter 2. The State of JavaScript

avaScript has not traditionally been considered a backend language; that space belonged to the likes of Java, Python, C/C++, C#/.NET, PHP, Ruby and so on. JavaScript was just a 'toy language' that allowed web developers to add animation to websites in order to improve its aesthetics. But this all changed with the advent of Node.js. With Node.js, developers can now write JavaScript code that executes on the server, as well as the client. In other words, developers can now write both front and backend code using the same language!

This provides huge productivity benefits, as common code can now be shared across the stack. Furthermore, developers can avoid context switching between different languages, which often breaks concentration and reduces output.

It also led to the rise in Isomorphic, or Universal, JavaScript frameworks, such as Meteor. These types of frameworks allow you to write applications entirely in JavaScript that run on both the client and the...

Evolution of the web application

When you type a URL, such as www.example.com, into your browser, what actually happens? First, the browser would send a request to one of Example Corp's servers, which retrieves the resource requested (for example, an HTML file), and sends it back to the client:

The browser then parses the HTML, retrieves all the files the web page depends on, such as CSS, JavaScript, and media files, and renders it onto the page.

The browser consumes flat, one-dimensional texts (HTML, CSS) and parses them into tree-like structures (DOM, CSSOM) before rendering it onto the page.

This scheme is known as the client-server model. In this model, most of the processing is handled server-side; the client's role is limited to simple and superficial uses, such as rendering the page, animating menus and image carousels, and providing event-based interactivity.

This model was popular in the 1990s and 2000s, when web browsers were not very powerful. Creating entire applications with JavaScript...

Benefits of Node.js

JavaScript is the language of the browser. There's no denying that. Next, let's examine the reasons why a developer should pick Node.js as the back-end language for their application. Although there are many reasons, here we've boiled it down to two factors—context switching and shared code.

Context switching

Context switching, or task switching, is when a developer is working on multiple projects, or in different languages, at the same time and has to switch between them regularly.

"Doing more than one task at a time, especially more than one complex task, takes a toll on productivity."                                               

                – Multitasking: Switching costs (American Psychological Association)

                     (http://www.apa.org/research/action/multitask.aspx)

Switching between projects

Programming is an activity that requires you to keep many variables in memory at the same time—variable names, interfaces of different modules, application structure...

Summary

In this chapter, we described the evolution of web applications from using the client-server model to SPAs, and how advances in JavaScript engines facilitated this transformation. Then, we discussed the benefits of using JavaScript across the stack, focusing on the topics of context switching and shared code.