var, let, const - Practicise

Introduction to JavaScript

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What is JavaScript?

Key Features of JavaScript

A Brief History of JavaScript

JavaScript in the Browser vs. Server (Node.js)

Setting Up JavaScript Environment

Why Learn JavaScript?

How to Add JavaScript?

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Inline JavaScript

Internal JavaScript

External JavaScript

Different Ways to Output Data

0/4

Using innerHTML

Using document.write()

Using window.alert()

Using console.log()

Variables and Constants

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var, let, const

Scope of Variables

Data Types

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Primitives Data Types

Non – Primitives Data Types

Operators

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Arithmatic Operator

Assignment Operators

Comparison Operators

Logical Operators

Bitwise Operators

Type Coercion and Conversion

Conditional Statements (if, else if, else)

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if, else if, else

Ternary Operator

Switch Statement

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What is Switch Statement?

Loops

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for…of and for…in Loops

Loop Control: break, continue

Functions

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What is Function ?

Function Declaration vs Function Expression

Parameters and Return Values

Default Parameters

Rest and Spread Syntax (…args)

Anonymous Functions

Arrow Functions

Higher-order Functions

Objects

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Creating objects

Accessing and Modifying Properties

Methods in objects

this Keyword and its Behavior

Object Destructuring

Arrays

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Array Declaration and Initialization

Accessing and Modifying Array Elements

Spread Syntax with Arrays

Array Destructuring

DOM Manipulation

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What is DOM Manipulation?

Selecting Elements

Changing Content and Styles

Adding and Removing Elements Dynamically

Events and Event Listeners

0/7

What is Events and Event Listeners?

Common Event Types and Practical Examples

Removing Event Listeners

Passing Parameters to Event Handlers

Event Delegation

Stopping Event Propagation

Classes in JavaScript

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Classes in JavaScript

Defining a Class

Objects in JavaScript

Real-World Example: User Class

Adding Getters and Setters

Inheritance in JavaScript

The this Keyword

String Functions in JavaScript

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String Functions in JavaScript

Number Functions in Javascript

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Number Functions in JavaScript

Error Handling in JavaScript

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Error Handling in JavaScript

try…catch Block

Throwing Custom Errors

Combining try…catch with Custom Errors

RegEx (Regular Expressions) in JavaScript

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Basic Syntax of Regex (Regex)

String Methods Using Regex

Patterns and Flags

JavaScript Modules

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What is JavaScript Modules & Why we use Modules?

Exporting in JavaScript Modules

Importing in JavaScript Modules

Combining Named and Default Exports

JavaScript Hoisting

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What is Hoisting and Types of Hoisting?

JavaScript JSON (JavaScript Object Notation)

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Key Methods of JavaScript JSON

JavaScript Style Guide

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Importance of a Style Guide

JavaScript Best Practices

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JavaScript Best Practices

JavaScript

About Lesson

var, let, const

JavaScript allows you to declare variables using three keywords: var, let, and const.

1. var:

It’s function-scoped, meaning the variable is accessible throughout the function in which it’s declared.
Variables declared with var can be re-declared and updated.

Example:

JavaScript

var age = 25;
var age = 30;  // Re-declaration is allowed
age = 35;  // Update is allowed

2. let:

Introduced in ES6, it’s block-scoped, meaning the variable is only accessible within the block ({}) in which it is declared.
Variables declared with let can be updated but cannot be re-declared within the same block.

Example:

JavaScript

let age = 25;
age = 30;  // Update is allowed

3. const:

Also block-scoped like let, but once a value is assigned to a const variable, it cannot be reassigned. It must be initialized at the time of declaration.

Example:

JavaScript

const age = 25;
// age = 30; // This will throw an error