.js Program Format

What is the Js file format?

Js stands for the Javascript file format. JavaScript is a lightweight, cross-platform, single-threaded, and interpreted compiled programming language. It is also known as the scripting language for web pages. It is well-known for the development of web pages, and many non-browser environments also use it.

We use a .js file extension to save the file and the JavaScript (JS) file is a collection of code intended for use on web pages. You can use the <script></script> tags to embed the JavaScript code inside the HTML document, or you can include a JS file. For code reuse, JS files can be included in multiple HTML documents, just like CSS files.

Example of Javascript code

Javascript

// JavaScript code to greet the user 
  
// Prompt the user for their name 
var userName = prompt("What is your name?"); 
  
// Check if the user entered a name 
if (userName !== null && userName !== "") { 
  // Display a personalized greeting 
  alert("Hello, " + userName + "! Welcome to the world of JavaScript."); 
} else { 
  // Handle the case where the user didn't enter a name 
  alert("Hello, anonymous! Welcome to the world of JavaScript."); 
} 

Output

What is your name?

Hello, Geek! welcome to the world of javascript

Features of the Javascript

• JavaScript is a text-based programming language. An integrated development environment (IDE) or a basic text editor can be used to create and edit the plain text code.
• It is an interpreted language, which means that an interpreter runs the code line by line. Unlike compiled languages, there is no separate compilation step
• JS is primarily used to enhance the interactivity and functionality of web pages. Web browsers have built-in JavaScript engines (such as V8 in Chrome and JavaScriptCore in Safari) that execute JavaScript code.
• It is commonly used on the client side to create dynamic and interactive user interfaces in web browsers.
• On the client side, JavaScript is often used to manipulate the Document Object Model (DOM), allowing dynamic updates to the content and structure of web pages.
• JavaScript is event-driven, allowing developers to respond to user interactions and system events. This is especially crucial in creating responsive and interactive web applications.

Applications of the Javascript

• Web Applications
• Android Development
• Server Applications
• Web Games

How to use JS files

You must include a JS file in the HTML document in order to use it. To include the file, use the link tag as indicated below.

<!--  <script src="site.js"></script>  -->

JavaScript Syntax

JavaScript files can contain variables, operators, functions, conditions, loops, arrays, objects, etc. Given below is a brief overview of the syntax of JavaScript.

• Var, let and const keyword is used declare variables.
• Supports arithmetic operators ( + – * / ) to compute values.
• Single line comments are added using // and multiline comments are added by /* and */.
• All identifiers are case-sensitive i.e. modelNo and modelno are two different variables.
• JS supports comparison operators like ==, != , >=, !==, etc.
• Classes can be defined using the class keyword.

Advantages of JS

• It always gets executed on the client environment to save lots of bandwidth and make the execution process fast.
• The biggest advantage of JavaScript having the ability to support all modern browsers and produce an equivalent result.
• JavaScript plays nicely with other languages and may be utilized in an enormous sort of application.

Disadvantages of JS

• The main problem or disadvantage in JavaScript is that the code is always visible to everyone anyone can view JavaScript code.
• JavaScript is usually interpreted differently by different browsers. This makes it somewhat complex to read and write cross-browser code
• If the error occurs in JavaScript, it can stop rendering the whole website. Browsers are extremely tolerant of JavaScript errors.

Conclusion

In summary, a JavaScript file (.js) contains code written in the JavaScript programming language. It is a versatile language that plays a crucial role in web development, both on the client and server sides. JavaScript files are executed by JavaScript engines, and the code within them is responsible for creating dynamic and interactive web experiences.

FAQs

Q1. What is the difference between == and === in JavaScript interview questions?

Ans: “==” is used to compare the only values and “===” is used to compare the values and type also.

Q2. What is scope in JavaScript?

Ans: It will determine the accessibility of variables.

Q3. What was the first name of JavaScript?

Ans: The original name of the JavaScript was Livescript.