Here is the Introduction of JavaScript:
JavaScript is a high-level, versatile, and dynamic programming language primarily known for its use in web development.
• It allows developers to add interactive and dynamic elements to websites, enhancing the user experience.
• JavaScript was initially created to make web pages interactive by enabling client-side scripting.
• It is a versatile language used for both front-end and back-end development.
Note: JavaScript syntax is similar to other C-style languages like Java and C++.
Features:
- Dynamic Typing: Variables can dynamically change their data types.
- Prototypal Inheritance: Objects can inherit properties and methods from other objects through prototypes.
- Functions as First-Class Citizens: Functions can be assigned to variables, passed as arguments, and returned as values.
- Asynchronous Programming: Supports asynchronous operations using callbacks, Promises, and async/await.
Usage:
- Client-Side Scripting: Used in web browsers to manipulate HTML, CSS, and handle events.
- Server-Side Development: With platforms like Node.js, JavaScript can be used for server-side scripting.
- Mobile App Development: Frameworks like React Native and NativeScript allow building mobile apps using JavaScript.
- Game Development: JavaScript is used for developing browser-based games.
Here’s a simple JavaScript code snippet that’s suitable for beginners.
// Prompt the user for their name
var userName = prompt("What's your name?");
// Check if the user entered a name
if (userName !== null && userName !== "") {
// Display a personalized greeting
var greeting = "Hello, " + userName + "!";
alert(greeting);
} else {
// Handle case where the user didn't enter a name
alert("Hello there!");
}
Adding JavaScript to a Page:
To add JavaScript to an HTML page, you can use the <script> tag. Here’s a simple example:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript Example</title>
</head>
<body>
<h1>JavaScript Example</h1>
<!-- Adding JavaScript within the HTML file -->
<script>
// Your JavaScript code goes here
document.write("Hello, World!");
</script>
<!-- External JavaScript file -->
<script src="script.js"></script>
</body>
</html>
Comments:
In JavaScript, comments are used to add explanatory notes or remarks within the code.
• Comments are ignored by the JavaScript interpreter and are not executed.
• They are solely for the benefit of developers to provide documentation and make the code more understandable.
There are two types of comments in JavaScript:
- Single-Line Comments
- Multi-Line Comments
Single-Line Comments:
Single-line comments are created using two forward slashes //. Everything after // on the same line is treated as a comment.
// This is a single-line comment
var x = 5; // This is an inline comment
Multi-Line Comments:
Multi-line comments start with /* and end with */. Everything between / * and */ is treated as a comment, and it can span multiple lines.
• Multi-line comments are often used for longer explanations, documentation, or for temporarily disabling a block of code.
/* This is a
multi-line comment */
var y = 10;
Example combining both types:
// This is a single-line comment
/*
This is a multi-line comment.
It can span multiple lines.
*/
var a = 42; // Another single-line comment