What is JavaScript? Summary of features and what you can do

In conclusion, JavaScript has great future potential… or rather, if you work in the web industry, you won’t be able to get a job without knowing JavaScript, so there is no loss in knowing it. You could say that knowing JavaScript prepares you to work in the web industry.

In this article, we will introduce the overview of JavaScript, its features, and what it can do.

Table of contents

  1. What is JavaScript?
  2. Features of JavaScript
  3. What you can do with JavaScript
  4. Is JavaScript a “better language to learn”?
  5. Where can I learn JavaScript?
  6. Summary: JavaScript is essential for the web industry

What is JavaScript?

JavaScript was developed as a client-side language in 1995 by a man named Brendan Icke.

The client-side language was born as a language for adding actions to websites, but it has been rapidly developed since then, and now it is used in fields such as smartphone application/game development and IoT with only JavaScript.

Server-side languages ​​are the opposite of client-side languages. A server-side language acts as a bridge between a client (browser, etc.) and a database on a website. Based on the request received from the client, I retrieve the value from the database, process it, and pass the result to the client. Examples include Java, Kotlin, Go, Python and PHP. (While JavaScript has a similar name to Java, a server-side language, they have nothing in common.)

Features of JavaScript

Feature 1. Good at asynchronous processing

Assuming that you have created a web service only with a server-side language, loading the web page will occur when you register the contents of the form in the database or refer to the database value (that spinning guy).
By using JavaScript’s “Ajax”, you can access the database without loading the web page, and you can achieve rich operations.

Feature 2. Although it is a client-side language, it can also be used on the server-side

As explained so far, JavaScript is a client-side language, but, by using a framework called “node.js” that appeared around the early 2010s, it became possible to develop the server-side in JavaScript as well.
In the past, it was common to use JavaScript on the client side and Java or Ruby on the server side, but recently, it is common for programs to be written in JavaScript everywhere in the system.

Feature 3. Has a powerful framework

JavaScript has frameworks such as React and Vue.js that greatly improve development efficiency and maintainability (programs are easy to read and fix).
In particular, React, developed by Facebook, is like a driving force that made it possible to create programs with a completely different method from conventional JavaScript development, and it is now the most used framework.

What you can do with JavaScript

I’ve introduced it here and there, but let’s summarize it here so that you can roughly understand what you can do with JavaScript.

What you can do #1. Bring your website to life

Naturally, JavaScript was originally developed to add movement to websites, but on the other hand, there is no language other than JavaScript (or AltJS, which is derived from it) that can add movement to websites (as far as I know).

What you can do 2. Event handling

An event is an action such as pressing a button, entering an email address in an input field, checking a checkbox, or pressing a tab.
By using JavaScript, for example, when you press a button, you can retrieve data from the database, or when you enter an email address in the input field, you can display “The email address is already in use” in real time.

What you can do 3. Create a smartphone app

JavaScript is used when adding actions to websites and creating web services, but it can also be used to create smartphone apps.
What’s more, smartphone apps originally need to be developed in different languages ​​for each OS, but with JavaScript (and HTML), you can create one program regardless of the OS (it’s called a hybrid app).

Is JavaScript a “better language to learn”?

Yes, you should study. It is no exaggeration to say that this is a “required subject”, especially for those who want to be active in the web industry or those who are already working in the web industry.

Looking at job postings on career change sites, it seems that Java is the most popular, followed by PHP, followed by JavaScript. I think it’s okay to take it as an assumption by the hiring side that they can at least change the behavior. So, it’s common to see job openings for “Java + JavaScript” even though they pretend to be using Java. It would be better to have a general understanding of how to use JavaScript and at least a library called jQuery.

Where can I learn JavaScript?

I said that JavaScript is a good language to learn, but where should I learn it?
Here are some websites where you can learn JavaScript for free.

dot install

It may be the first site you go to when it comes to learning programming. It is a very famous programming video learning site.
Starting with pure JavaScript, we have the necessary knowledge for those who want to work with JavaScript, such as the library jQuery, the framework React, and Vue.js.
If you can absorb everything you can learn with dot install, that alone is more than enough for an introductory course, so I recommend that beginners start with dot install first.


Progate is a hands-on programming learning site (a format where you can learn while actual programming).
It is a learning site mainly made for people who want to create web services.
Progate also offers a paid version of the course called Progate Plus. If you get used to learning with Progate, you may want to try the paid version as well.

Tohoho’s Introduction to WWW

This is a programming learning site where useful information for developing web services is summarized in text format.
Since the information is only summarized in text format, there is no richness such as videos or hands-on, but for that reason “the amount of information is incomparably large”.
I want to learn JavaScript deeply! It is recommended for anyone who wants.

Summary: JavaScript is essential for the web industry

By reading this page, I hope you have understood how important JavaScript is as a programming language.
It is necessary when developing websites and services, so it is a good idea to learn from the sites listed above.

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