The most complete guide to JavaScript for website developers

The most complete guide to JavaScript for website developers

Everyone who has even basic knowledge about how websites work has heard about JavaScript. This scripting language was created to give more dynamism to websites and, thanks to its versatility, extensive community, variety of libraries, and frameworks, it has become a solution for different types of applications.

The developer who specializes in this language becomes a complete professional. One of the main people responsible for JavaScript’s change in status, from a client-side language to a comprehensive solution, was the Node.js interpreter, which allowed its use on the server side and enabled the creation of complete websites.

In this post, we will learn what the JavaScript language is, its applications, main libraries, and frameworks, and why it is growing more and more. Check out!

What is the JavaScript language?

JavaScript is a language that allows the insertion of functions into a web application, that is, it allows a website to be more than a static and informative page. With JavaScript, it is possible to update content on a page at intervals and create interactive maps, and animated graphics, among other resources.

In the structure of a website, that is, in its code, JavaScript is in the third layer, below HTML and CSS. See below the order and what each of these layers represents.


HTML is the markup language, that gives the structure to the page, and its skeleton. Here the positions of each element of the website are indicated: paragraphs, tables, lists, titles, insertion of images, and videos.


CSS is a language that defines the style rules that will be used on a page. Here the colors and style of fonts, background, content positioning in columns, and even element transition rules are defined.

After all, what is the role of JavaScript on a website?

We saw above that websites are structured into three layers, two of which were briefly explained in the previous topic. Let’s understand the JavaScript layer in more detail and how it relates to the others. First of all, we need to understand how the code is interpreted, so that the image and resources that the user sees on the screen when accessing a website are displayed.

When we open a website in our favorite browser, we are implementing code within an execution environment. The JavaScript language is triggered by the browser’s rendering engine, after interpreting the HTML and CSS — this ensures that the page structure will be ready when the JavaScript is executed.

These actions also ensure that the main content of the page will be available as if JavaScript were loaded before HTML and CSS, IT errors could occur that would compromise the entire structure. As it is a language created to give dynamism to the page, JavaScript was initially focused on being a language that ran on the client side, that is, in the browser, but this limitation has now been broken. See how this is done in the next topic.

How did the JavaScript language stop being just client-side?

When we talk about creating websites, we have to specify which side of the application we are referring to — there are two, the server-side and the client-side, that is, the content that appears in the browser. Client-side codes — created in HTML, CSS, and JavaScript — run in the user’s home, in their browser. Server-side codes are executed on the server where the website was hosted.

Although it was created to act on the client side, JavaScript can currently be used on both sides, including the server side. This allows a developer specialized in this language to work on all stages of creating a web application. These developers are called full-stack devs and are increasingly valued in the market.

What are the technologies that allow the use of full-stack JavaScript?

So that we can better understand how JavaScript is used in all layers of a web application, we need to know the following technologies — Node.js, Express, EJS, and MongoDB — as they are what allow the creation of a website from start to finish with JavaScript.


If today we can build a website from start to finish using JavaScript, we have to thank programmer Ryan Dahl. The Node.js platform makes it possible to interpret server-side code, bringing JavaScript to the backend.

When creating a development environment, the developer team must install Node.js and then a tool called NPM — Node Package Manager. It is NPM that will allow you to install and manage modules in Node.js. Some developers prefer Yarn to NPM, but the important thing is not the tool itself, but its functionality, more specifically, the installation of the Express framework.


Express allows you to create any type of web application with ease, as we are talking about a minimalist and robust platform. With it, you can easily move from the browser to the back-end, saving programming work.


EJS — Embedded JavaScript templates — is a language that allows the creation of HTML using only JavaScript. In other words, with it, the programmer can create the entire website using just one language. Thus, the developer gains in creation speed, in addition to the code being more integrated and standardized.


MongoDB is the tool that completes the creation of an end-to-end website using only JavaScript, as it allows the structuring of the database into JSON-like files. It is an open-source and free database, which should be used with the other tools indicated in this topic.

Besides websites, what can we do with JavaScript?

Despite always being related to websites and web applications, the JavaScript language has become increasingly versatile in recent years. This change began to happen in the early 2000s, when Google adopted the language to develop some of its products, such as Gmail. At this time, developers encountered a big problem: browsers’ JS interpreters were still quite slow.

To overcome this situation, the company developed an open-source JS engine — Engine V8 — and placed it as standard in its browser, Google Chrome. It didn’t take long for the engine to become a market standard and be adopted by other browsers.

From this, with the growth of the community of developers specializing in JavaScript, new tools emerged and the language began to be used to develop solutions that go far beyond web applications.

See below what can be done using the JavaScript language.

Mobile Applications

JavaScript allows the creation of applications for smartphones, with the advantage that the developer can use only one language on different platforms. It all started with hybrid applications, which have this name because they use two different technologies.

For example, the Android Operating System is written in Java. When using Cordova, the programmer can create common web applications, using the HTML, CSS, and JavaScript structure, and access the mobile device’s functionalities through JavaScript, through integration with the native Java code.

When we open the application, we are opening the internal browser, which will display the application and allow access to these features. The hybrid name comes precisely from this combination of web technology and native technology.

There is also the possibility of developing native applications, using React Native and NativeScript tools. In this model, instead of creating an HTML screen, XML styled with CSS is used. Instead of using the standard browser as a base, in this model, a screen native to the platform — iOS or Android — is created with the actions written in JavaScript.

The great advantage of native applications over hybrids is that the first delivers greater performance than the second. Hybrid applications depend on the system’s default browser, which creates a risk of code incompatibility. In the native application, there is no dependence on browsers, meaning the developer will not need to worry about whether or not the features will be supported.

Desktop Software

Yes! It is possible to create desktop applications using JavaScript, taking advantage of Chromium — the open-source browser that serves as the basis for Google Chrome — in addition to Node.js. In this application model, the screens are created using HTML5 and CSS3, in addition to JavaScript, which communicates directly with Node.js, which will be embedded in the application.

The most used framework for this type of application is Electron, created by the GitHub team. With it, software such as Atom, Slack, and Visual Studio Code have already been developed.


If we can create software for desktops and mobile devices, we can also create complete games based on the JavaScript language. There are Frameworks specialized in creating games. One of the most used frameworks for this objective is Phaser, which allows developers to use a trio of languages ​​— HTML, CSS, and JavaScript — to create games.

One of the benefits of using Phaser is that the company itself offers a complete game development course for anyone who wants to develop games using its platform. The course goes from “Hello, World” to the development of a complete game. Furthermore, for those who decide to invest in the engine as a work tool, the official Phaser website has a store with countless plugins, apps, and courses that teach how to use the platform and develop games.

What is needed to learn JavaScript?

The JavaScript language is one of the most sought-after by those who want to learn programming. This is no coincidence, after all, we are talking about an extremely versatile language that allows developers to create applications for different environments, often with just one code.

To be a good JavaScript developer, the apprentice must also seek knowledge in HTML and CSS, taking advantage of the countless materials, forums, and repositories on web development. Furthermore, you must know programming syntax to create standardized, clean, and lightweight code.

What is programming syntax?

The programming language doesn’t have that name for anything. We are talking about a language, which has structure and syntax, with a set of commands, commas, periods, special characters, and well-defined rules about what can and cannot be done. If in human language syntax errors generate communication failures, in a programming language, a syntax error can mean a program with bugs.

Contrary to what many people might think, to study programming you don’t need to be a math genius or a technology expert. A good programmer is a good problem solver, that is, a person who can divide the solution of a problem into well-structured steps.

This can be done with paper and pen or with a computer, it doesn’t matter, the important thing is that the person describes all the steps to perform a task. After that, you must instruct the computer, through a programming language, to perform these tasks, sequentially and logically — this is what we call programming logic.

There are programming logic courses, which teach how to create algorithms and also how to structure them into codes, which can then be transported to your preferred programming language, such as JavaScript.

Can I learn JavaScript and programming for free?

There are no excuses for anyone who wants to learn to program. A range of free programming courses are available on the internet, for both beginners and intermediate programmers. Some of them are even of higher quality than paid courses. Among so many options, we can highlight two: Instituto TIM and Canal Curso em Vídeo, by Professor Gustavo Guanabara. Below we have separated some courses from the two platforms that are related to the topic of this post.

Video Course

The Curso em Vídeo channel offers various training courses focused on programming and technology, with excellent teaching and a professional graphics package, superior to many paid courses. See some options below:

  • programming logic course — learn programming syntax and write your first codes;
  • JavaScript course for beginners — after learning to program, it’s time to transfer your knowledge by learning the basics of JavaScript ;
  • HTML with CSS course — what would JavaScript be without its two battle friends, HTML and CSS? To be an expert in JavaScript you will have to learn them too;
  • object-oriented programming course — this course will teach you how to create codes and programs with a pluggable structure, that is, it will be possible to create separate codes, combine them in one program, and then reuse them in another.

TimTec Courses

The TimTec Institute offers a series of courses focused on the world of technology and web content production. For those who want to dedicate themselves to development, whether of websites, mobile applications, or games, the courses below are the most suitable. Look:

  • HTML5 Introduction to the front-end — the HTML5 course is the first step for anyone who wants to create a website or application based on JavaScript;
  • introduction to programming logic — learn programming syntax;
  • JavaScript course and its libraries — JavaScript course focusing on the jQuery library;
  • game programming course with JavaScript — a course with a practical focus, that is, you learn by creating a game;
  • game designer course — where the student will learn the basic concepts for creating the game, which involves mechanics, phase structuring, objectives, challenges, etc.;
  • introduction to website creation — here you will learn how to create your first website;
  • front-end development — a course that covers the creation of websites with a focus on the client side, that is, HTML5, CSS3, and JavaScript;
  • interface development with CSS3 — a course focused on CSS, so you understand the importance of the style language to make the website lighter and more responsive;
  • web development with Angular JS — development using one of the main frameworks on the market;
  • good practices for software development — a very important course for those who are starting in programming and want to create syntactically correct code.

What are the main JavaScript frameworks and libraries?

As we have already seen in this post, development with JavaScript can be enhanced with the help of libraries and frameworks. These tools allow a scripting language, created for client-side development, to be used to program products for the most diverse platforms.

The JavaScript library uses code as a base and a certain implementation of rules, with a focus on simplifying the use of a language. The framework is a set of components that have a ready-made basis for a project. See below which are the main JavaScript libraries and frameworks.


React is a very popular framework, maintained by Facebook and is considered much more than a framework, a library. Using React is almost always related to other libraries, such as Redux. Among the main features of this framework is the presence of clean and reliable code, featuring simplified abstraction layers.

Another feature that we can highlight is the Virtual DOM, which allows the developer to make changes to the code and insert them into the page’s DOM in a more controlled way. Regarding the database, React operates in a unidirectional flow, also known as one-way data binding. In this model, the information comes directly from the database and goes to the screen, without synchronization, that is, the system reads the data and displays it on the screen.


Just as Facebook maintains React, Google maintains Angular, one of the most complete frameworks on the internet, which is in its eighth version. Since its launch, Angular has received numerous improvements focused on optimizing the user experience and reliability of its information database.

Regarding data, Angular works differently from React, presenting a flow known as two-way data binding. Here there is greater synchronization of data with the front-end elements developed by the programmer, simplifying communication between the database and the product.


Vue.js is a library recommended for those just starting in the world of programming with JavaScript. The library presents templates based on HTML and operates on a two-way data binding system. The main advantage of Vue.js is its simplicity of use, with an intuitive interface that makes learning the language simplified, that is, ideal for beginners.


jQuery is the most popular JavaScript library and is almost a basic requirement when a company is looking for a professional who can master the language. jQuery’s motto already says its intention: “Write less, do more”, “Write less, do more”.

The benefit of this library is in simplifying native language codes, which tend to be much more extensive. In addition to making typing easier, and speeding up development, jQuery users create cleaner, more organized, and easier to maintain code.

Due to its popularity and extensive community, jQuery has become the library with the largest number of plugins and other derived libraries, of which we can highlight jQuery Mobile and jQuery UI.

Are Java and JavaScript the same thing?

Because of the similar name, many people confuse Java and JavaScript. The truth is that this similarity is only in the name and syntax — the two languages ​​have similar mathematical and control structures. But the name similarity is not by chance, it has a historical reason.

The JavaScript language was commissioned by Netscape and created by developer Brendan Eich in mid-1995. In principle, the name of the language was LiveScript. Later, Netscape sought partnerships to run the project and received support from SUN Microsystems, owner of the Java language. The change from LiveScript to JavaScript was made at this stage, as a marketing strategy. After all, the Java language was in evidence.

Differences between the two languages

But if the similarities are only in the names, history, and syntax, what are the differences between the two? First, it is necessary to make it clear that JavaScript is not a traditional programming language — it cannot be compiled and executed later. We are talking about a scripting language, as it depends on a browser to function.

The Java language is a programming language that produces independent software, that is, programs that do not depend on platforms to function. Applications are executed by the Java virtual machine and then run on the operating system in which it is installed.

As we saw in this post, the JavaScript language began as a simple way to bring more life to a website. Every year, it becomes a more complete and versatile language, capable of doing almost everything that more traditional languages ​​can. The professional who specializes in it will certainly have a large market to explore.

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