Variables and Data Types

Here is the description of Variables and Data Types:

Variables are Containers for Storing Data.

• In JavaScript, variables are used to store and represent data values. Variables provide a way to label and reference data in your programs.

Variable Declaration:

Variables are declared using the var, let, or const keyword. In modern JavaScript, it’s recommended to use let and const for variable declarations.

let myVariable; // Declaration using let
var anotherVariable; // Declaration using var
const constantVariable = 42; // Declaration using const (immutable)

→ var:

• Variables declared with var have function scope or global scope.
• They can be re-declared within the same function or block.
• They can be updated.

function exampleVar() {
  var x = 5;
  var x = 10; // Re-declaration is allowed

  if (true) {
    var x = 20; // Updated
  }

  console.log(x); // Output: 20
}

→ let:

• Variables declared with let have block scope.
• They cannot be re-declared in the same scope.
• They can be updated.

function exampleLet() {
  let y = 5;
  // let y = 10; // Error: Cannot redeclare 'y' in the same scope

  if (true) {
    let y = 20; // Different block scope
    console.log(y); // Output: 20
  }

  console.log(y); // Output: 5
}

const:

• Variables declared with const have block scope.
• They cannot be re-declared or updated.

function exampleConst() {
  const z = 5;
  // const z = 10; // Error: Cannot redeclare 'z' in the same scope
  // z = 15; // Error: Cannot update 'z'

  if (true) {
    const z = 20; // Different block scope
    console.log(z); // Output: 20
  }

  console.log(z); // Output: 5
}

Variable Initialization:

Variables can be assigned values during or after declaration.

let myVariable = "Hello, World!"; // Initialization with a string
var anotherVariable = 10; // Initialization with a number

Data Types:

JavaScript has several data types that can be categorized into two main groups:

• Primitive data types
• Object data types

7. BigInt:

Object Data Types:

• Object
• Array
• Function
• Date

Object:

Represents a collection of key-value pairs.

Examples:

let person = {
  name: 'John',
  age: 25,
  city: 'New York'
};

Array:

Represents an ordered list of values.

Examples:

let fruits = ['apple', 'banana', 'orange'];

Function:

Represents a reusable block of code.

Examples:

function greet(name) {
  return 'Hello, ' + name + '!';
}

Date:

Represents a date and time.

Examples:

let today = new Date();