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Chapter 1 - Basics of Java Script Programming
For MSBTE Diploma CO / IT / AIML Branch
What is scripting language ?
A scripting language is a programming language designed to automate tasks or execute commands within a larger software environment. Unlike compiled languages, scripting languages are typically interpreted, meaning their code is executed line by line by an interpreter, without the need for prior compilation into machine code.
Key characteristics of scripting languages:
- Interpreted: Scripting languages are usually executed by an interpreter at runtime.
- High-level: They provide a higher level of abstraction, focusing more on ease of development and task automation.
- Embedded Usage: Often embedded within larger applications to control certain aspects or automate repetitive tasks.
- Dynamic Typing: Variables can be created without defining their types, allowing for more flexibility.
- Ease of Use: They are generally easier to learn and use, with simpler syntax compared to system programming languages.
Common examples:
- JavaScript (for web development)
- Python (for automation, web development, and data analysis)
- Bash (for shell scripting)
- Ruby (for web development and automation)
- PHP (for web server scripting)
Features of Java Script -:
JavaScript is a powerful, lightweight, and widely used scripting language primarily used for web development. Here are some key features of JavaScript:
1. Interpreted Language:
- JavaScript is an interpreted language, meaning it doesn’t need prior compilation. The browser interprets and runs the JavaScript code directly, which allows for real-time execution and dynamic interaction on web pages.
2. Client-Side Scripting:
- JavaScript is predominantly used as a client-side scripting language. It enables developers to create dynamic content, handle user interactions, and update web pages without reloading the entire page (using techniques like AJAX).
3. Object-Oriented:
- JavaScript follows an object-based approach, allowing for the creation and manipulation of objects. It supports features like inheritance, encapsulation, and polymorphism, though its object-oriented structure is prototype-based, rather than class-based like other languages.
4. Event-Driven Programming:
- JavaScript supports event-driven programming, allowing code to respond to user actions such as clicks, form submissions, mouse movements, and keyboard inputs.
5. Dynamic Typing:
- JavaScript is dynamically typed, meaning that variables don’t require explicit type declarations. A variable’s type is determined by the value assigned to it and can change at runtime.
6. Asynchronous Programming:
- JavaScript supports asynchronous operations, such as AJAX requests or promises, allowing tasks to run in the background without blocking the main program execution. This helps create smooth and responsive user interfaces.
7. Cross-Browser Compatibility:
- JavaScript is supported by all modern web browsers (Chrome, Firefox, Safari, Edge, etc.). It provides consistent behavior across different platforms and environments, though there can be minor compatibility issues that developers need to address.
8. First-Class Functions:
- Functions in JavaScript are treated as first-class citizens, meaning they can be stored in variables, passed as arguments to other functions, and returned from functions. This feature is heavily utilized in JavaScript’s functional programming style.
9. Lightweight and Versatile:
- JavaScript is lightweight and can be embedded directly into HTML pages, providing a high level of interaction and control over web content without significantly increasing the page’s size or complexity.
10. Prototypal Inheritance:
- JavaScript uses prototypes for inheritance, which allows objects to inherit properties and methods from other objects. This approach is more flexible than traditional class-based inheritance in some cases.
11. DOM Manipulation:
- JavaScript can manipulate the Document Object Model (DOM) of a web page. It allows developers to dynamically add, remove, and modify HTML elements and attributes, enabling real-time updates to the user interface.
12. Versatile Ecosystem:
- JavaScript has a vast ecosystem with frameworks and libraries like React, Angular, Vue.js, Node.js, and Express, which extend its capabilities for building full-scale web applications, server-side solutions, and mobile apps.
How to write Java Script document -:
To write JavaScript code within an HTML document, you use the <script> tag. JavaScript can either be included directly within the HTML file or linked externally via a separate .js file. Below are the steps and examples for both approaches:
1. Inline JavaScript in HTML
You can write JavaScript directly inside the HTML document by placing the code within the <script> tag, either in the <head> or <body> section.
2. External JavaScript File
For better code organization, you can write your JavaScript code in a separate .js file and link it to the HTML document using the <script> tag with the src attribute.
Step-by-Step Guide:
- Create an HTML file (e.g.,
index.html). - Create a JavaScript file (e.g.,
script.js). - Link the JavaScript file in the HTML using the
<script>tag.
Data types used in Java Script -:
JavaScript provides a variety of data types that are divided into two categories: primitive data types and non-primitive (reference) data types. Understanding these data types is essential for effective programming in JavaScript.
1. Primitive Data Types
Primitive data types are basic types of data that are not objects and represent a single value. These data types are immutable, meaning their values cannot be altered once defined.
2. Non-Primitive (Reference) Data Types
Non-primitive data types are more complex and are objects or references to memory locations. These data types can hold collections of values and are mutable.
Variables in Java Script -:
In JavaScript, variables are containers used to store data values. Variables can be declared using the keywords var, let, or const, each with its own scope and behavior.
1. Declaring Variables in JavaScript
var
- Used to declare variables globally or function-scoped.
varallows redeclaration of the same variable within the same scope.- Variables declared with
varcan be updated and initialized later
let
- Introduced in ES6,
letis block-scoped, meaning it is only accessible within the block (e.g., inside{}) where it is declared. letdoes not allow redeclaration in the same block, but it can be updated.
const
- Also introduced in ES6,
constis used to declare variables with constant values that cannot be reassigned or redeclared. - Like
let,constis block-scoped. - Important: Objects declared with
constcan still have their properties updated, though the reference to the object cannot be changed.
Keywords in Java Script -:
A keyword in JavaScript is a reserved word that has a special meaning in the language. These words are part of the JavaScript syntax and cannot be used as identifiers (e.g., variable names, function names, or other names). Keywords are used to perform specific operations, control the flow of the program, declare variables, define functions, handle errors, etc.
Characteristics of JavaScript Keywords:
- Predefined: They are predefined in JavaScript, meaning they are built into the language.
- Syntax Control: Keywords define the structure and flow of the program (e.g.,
if,for,function). - Not Reusable: You cannot use them to name variables, functions, or classes because they are reserved for the language’s built-in functionality.
Operators in Java Script -:
In JavaScript, operators are symbols or keywords used to perform operations on operands (variables, values, or expressions). Operators are essential for manipulating data and controlling the flow of a program.
Types of Operators in JavaScript:
Arithmetic Operators
Perform mathematical operations on numeric values.
2. Assignment Operators
Assign values to variables.
Comparison Operators
Compare two values and return a Boolean (true or false).
Logical Operators
Combine or invert Boolean values.
Bitwise Operators
Perform bit-level operations on integers.
Ternary/Conditional Operator
The ternary operator is a shorthand for an if-else statement.
end of part 1 -------->
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