Explain JavaScript Data Types

JavaScript has several data types that are used to represent different kinds of data. These data types can be broadly categorized into primitive types and objects. Here’s an overview of each data type with examples:

1. Primitive Data Types

a. Number

Represents both integer and floating-point numbers.

let age = 25;
let price = 19.99;
console.log(typeof age); // "number"
console.log(typeof price); // "number"

b. String

Represents a sequence of characters.

let greeting = "Hello, World!";
console.log(typeof greeting); // "string"

c. Boolean

Represents a logical entity and can have two values: true or false.

let isAvailable = true;
let isClosed = false;
console.log(typeof isAvailable); // "boolean"
console.log(typeof isClosed); // "boolean"

d. Null

Represents the intentional absence of any object value. It is treated as a falsy value.

let emptyValue = null;
console.log(typeof emptyValue); // "object" (this is a known bug in JavaScript, it should be "null")

e. Undefined

A variable that has been declared but not assigned a value.

let notAssigned;
console.log(typeof notAssigned); // "undefined"

f. Symbol

A unique and immutable data type often used to identify object properties uniquely.

let sym = Symbol('unique');
console.log(typeof sym); // "symbol"

g. BigInt

Represents integers with arbitrary precision.

let bigIntNumber = 1234567890123456789012345678901234567890n;
console.log(typeof bigIntNumber); // "bigint"

2. Object Data Type

Used to store collections of data and more complex entities. Objects can contain properties and methods.

a. Object

Represents an instance through which we can access members.

let person = {
    name: "John",
    age: 30
};
console.log(typeof person); // "object"

b. Array

A special type of object used for storing ordered collections.

let numbers = [1, 2, 3, 4, 5];
console.log(typeof numbers); // "object"

c. Function

A callable object that can be defined using a function declaration or expression.

function greet() {
    return "Hello, World!";
}
console.log(typeof greet); // "function"

d. Date

Represents a date and time.

let now = new Date();
console.log(typeof now); // "object"

e. RegExp

Represents a regular expression.

let pattern = /ab+c/;
console.log(typeof pattern); // "object"

Example Output

Here’s an example script that demonstrates the use of various data types and outputs their types:

let age = 25;
let price = 19.99;
let greeting = "Hello, World!";
let isAvailable = true;
let emptyValue = null;
let notAssigned;
let sym = Symbol('unique');
let bigIntNumber = 1234567890123456789012345678901234567890n;
let person = { name: "John", age: 30 };
let numbers = [1, 2, 3, 4, 5];
function greet() { return "Hello, World!"; }
let now = new Date();
let pattern = /ab+c/;

console.log(typeof age);           // "number"
console.log(typeof price);         // "number"
console.log(typeof greeting);      // "string"
console.log(typeof isAvailable);   // "boolean"
console.log(typeof emptyValue);    // "object"
console.log(typeof notAssigned);   // "undefined"
console.log(typeof sym);           // "symbol"
console.log(typeof bigIntNumber);  // "bigint"
console.log(typeof person);        // "object"
console.log(typeof numbers);       // "object"
console.log(typeof greet);         // "function"
console.log(typeof now);           // "object"
console.log(typeof pattern);       // "object"

By running this script, you’ll see the type of each variable output to the console, demonstrating the different data types available in JavaScript.