What Is JavaScript Used For? Complete Guide About JavaScript

JavaScript is a text-based client-side scripting language used to control and create the content of dynamic web pages. It allows you to implement dynamic features on a web page that cannot be done just using HTML and CSS i.e., click to show dropdown menu, image moves, autocomplete text suggestions, animated graphics, interactive forms, update the content without reloading a web page manually and lot more.

However, Do you still want to ask the question, ‘What is JavaScript used for?’

Power of HTML, CSS, and JavaScript:

When most people start learning code, they start with HTML and CSS. After learning, they go into JavaScript. This means that all three languages together form the backbone of web development.

  • HTML: HTML (Hypertext Markup Language) is used to structure the web pages and their content For example, create headings, content structured within paragraphs, add images to the content, structure the data into bulleted points, using data tables.
  • CSS: CSS (cascading style sheet) is used to present web pages, including layout, font style, and color. This allows one to adapt the presentation to a variety of devices, such as computer screens, mobile screens, or printers. CSS is independent and can be used with any XML-based markup language.
  • JavaScript: JavaScript is the third element. Once you have created your HTML and Aesthetic Web (CSS) structure, JavaScript will animate your site or project and makes it dynamic.

What is JavaScript used for?

We have covered this a bit in the introduction, but here is a quick list of the important things to use for JavaScript.

Make webpages Interactive ­— if you want to make your website more than a static page, you need to add some JavaScript code to it. There are unlimited things you can do with the help of JavaScript on your web pages like:

  • Show 2D/3D animations.
  • Show or Hide the information with a click on a button.
  • Showing dropdown menus.
  • Zooming in or out of the image.
  • Display counter on the web page, and a lot more.

Creating mobile apps — JavaScript is not just for website development. It also created apps that you have installed on your mobile phone or table.

Developing Web Browser games — maybe you played a game directly on the browser? JavaScript is also used to develop the web browser based games.

As a Backend web development programming language —Yup, JavaScript is used in both frontend and backend development. It allows its users to create the web servers and the backend infrastructure using Node.js.

How does JavaScript work in a browser?

What Is JavaScript Used For? How does JavaScript work in a browser?

Whenever we run a JavaScript code in web browser, the code goes to the browser’s engine and the engine runs the source code to get the output.

The main advantage of JavaScript code is that it supports almost all web browsers. So, you don’t have to worry about whether your site visitor uses Google Chrome, Internet Explorer, Firefox, Bing, or any other browser. Also JavaScript supports all operating systems including Linux, Mac OS, or Windows.

Some web browsers with their JavaScript engines are as follows:

Web BrowsersJavaScript Engines
SafariJavaScript Core
ChromeChrome V8
FirefoxSpider Monkey

What is Vanilla JavaScript?

What is Vanilla JavaScript? What Is JavaScript Used For?

Vanilla JavaScript is a name for using simple JavaScript without additional frameworks or libraries such as React, Vue, or jQuery.

JavaScript Frameworks:

The JavaScript framework is a collection of JavaScript libraries that provide developers with pre-written code to use for routine programming tasks.

Developers can use multiple JavaScript frameworks and libraries to build websites. Some of the popular JavaScript frameworks include Vue.js, React, jQuery, Angular, and React Native, Node.js

Tools you need to run JavaScript Code:

To execute the JavaScript code you will need a text editor to write the code and a web browser to see the output. You can use any text editor that suits your personality, such as Atom, VS Code, Notepad ++, or any other. I recommend the VS-code because it’s open-source and very comfortable to use. You can also use any web browser, including Chrome, Firefox, Bing, Internet Explorer, etc.

How to add JavaScript to your Website?

Adding JavaScript code to a web page is a very simple process. Like CSS, JavaScript can be used in HTML in a variety of ways, such as:

1) Inline JavaScript:

You can add JavaScript code to HTML tags in certain JS-based attributes. For example, HTML tags have event features that allow you to run code inline when an event is triggered.

<input type="button" value="Login" onclick="login()">

2) Internal JavaScript:

Like the style tag to declare in HTML pages, script tag is used for JavaScript.

For Example:

function showAlert(){
	alert('Alert is triggered inside the js function')

3) External JavaScript:

May be you have the JavaScript code in another file. You can also add it in  your HTML page.

Check the example below:

console.log('This is external.js file')

<!-- index.html -->
<script src="./external.js">

The “src” attribute of script tags allows you to apply a source for JavaScript code. This reference informs the browser to fetch the contents to the external.js.

external.Js file can be indexed in the same directory with HTML, or it can be retrieved from another site. For fetching the data to another site, you will need to pass the full URL like (http: //…/external.js).

.js is an extension of JavaScript files, such as HTML.

Now that we’ve considered ways to add JavaScript code into our HTML code, now let’s take a look at the data types in JavaScript.

Data Types in JavaScript:

What Is JavaScript Used For? Types of JavaScript

Before discussing the data types in JavaScript we need to know, what are the data types?

Data types are the attributes that tell the interpreter or compiler what the programmer intends to use the data. Most languages support basic data types like integers, floating, and Booleans.

Here are some basic types of data that JavaScript supports:

1. Number:

The number is the most basic data type of JavaScript that supports almost all programming languages. The data type only includes numbers like 1,9.2,3, and so on. This allows you to perform arithmetic operations such as addition, subtraction, multiplication, and many more.

2. String:

The string is the most commonly used data type in programming languages. Includes all characters (long or short sentences) such as “JavaScript is the best programming language”.

All characters and phrases that are in the string data type should be written in double quotes (“—“), single quote (‘—‘), or in backticks (`—`). There is no difference between double and single quotes, but backticks have more features like:

  • Add variables to the sting, such as `I am from $ {country}`. Here the country is the name of the variable is used directly in the string.
  • Support multi-line sting. With common quotes(single or double) you needed to add the escape character inside the string to move the string to the new line, but in the case of backticks, you can move the string to the new line just press the Enter button. ForExample:
var newStr= `This is a
Multiline string`

3. Boolean:

 Boolean is the simplest type of JavaScript. It can only be two values: True (yes) or False (no).

4. Array:

The data type supports all types of data, meaning you can store any type of value in it including a number, string, boolean, or array inside the array (child array).

For Example:

[2,5, "programming", [1,2,4]]

Each value in an array is separated by a comma (,). The index of the array always starts at zero (0).

5. Object:

An object is an abstract data type. The data in the object is stored in the form of a key: value pair. The key must be a string and the value can be of any type, including the object inside the child object. You can use the key to access the content inside the object.

For example:

{"Name": 'Programmer', "Country": "United States", "Age" : 22

This object will return “programmer” to us.

6. NULL:

NULL is also the data type that supports NULL. This means that there is no real value exists. It has value but it’s not real.

7. Function:

Function is the type of data in JS. Functions contain a block of code that we can call anywhere in the code.

For Example:

Function add(a,b)
    return a+b;

Variables in JavaScript:

Variables are containers that contain values for any data type. They also provide descriptive names for the data, so our programs and readers can be understood more clearly.

JavaScript provides three ways to declare variables, let’s see the difference between them:

1. Var:

Var is the oldest and most basic method of declaring a variable. The values ​​assigned to the variable that is declared using the “var” operator can be changed later in the code.

For example:

Name = “programming language”

Name = “language”

2. Let:

Let method is also very similar to Var. But the main difference is that the variable declared with the let operator has only the scope of the immediate closing brackets {}.

For example:

Function chk ()
   var a = "JS"
   let = "programming"
console.log (a, b) // JS programming
var c = "PHP"
let d = "language";
Console.log (c); // PHP
Console.log (d) // Reference error
chk ()

3. Const:

The value stored in the variable which is created by the const operator cannot be reassigned to another value.

For example:

var name = "Programming"
Name = "language" // No error

const city = "California"
City = "New York" // Error! Value cannot be reassigned.

Why do developers prefer JavaScript over other programming languages?

  • Huge Community.
  • Native to web browsers.
  • Easy to learn as compared to other programming languages.

Pros and Cons of using JavaScript:

Quick Feedback to Visitors: JavaScript is very fast and they don’t have to wait to reload the page to see if they forgot to enter Not Support every features: We cannot use JavaScript to create a web or app related to networking, as it does not have such features.
Less Load on Web Server: It allows its users to verify input before sending to the server such as email format, or check the special characters included in the password before submitting the Sign-Up form, etc. This saves a lot of server traffic which means less load on the server.Not support read-write at client Side: JavaScript does not allow read or write files on the client-side.
Enhance Interactivity: JavaScript provides its users with a variety of useful features that enhance interactivity.
For example: when the user clicks the login button. Loading animation is shown until the login function executes completely, or showing the ripple effect when clicking on the button, and many more.
Lacks Multithreading and processing: JavaScript doesn’t support multithreading and multi-processor capabilities.


We hope the article meets your needs. Our goal is to provide insights into the JavaScript programming language we have done thorough research on every aspect and then started writing an interesting and comprehensive article in an informative tone.

There are many more features in JavaScript that we can discuss, but I hope this article provides you with a clear vision for moving forward. Now you need to know what the language is and how you can use it on the website.

In this article, we’ve looked at what is JavaScript used for, how to include JavaScript code in your HTML files, popular JavaScript frameworks, various JavaScript data types, variables that act as containers for data, and also discuss the pros and cons of using JavaScript language.

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