datatype.md

Datatypes

Datatypes are the type of data a variable can store

• Primitive types
• Reference types

🧱 Primitive Types

Type	description	Example
Number	Both integers and floating-point numbers (Number literal)	5, 5.55, Infinity, NaN
String	Textual data wrapped in quotes (String literal)	"Hi", 'Hi', `Hi`
Boolean	Logical values: true or false	true, false
Undefined	A variable that has been declared but not assigned	undefined
Null	An intentional absence	null

Example

let age = 15;
let name = "Rohan";
let isAdult = false;
let Lisence = undefined; // When it is not needed when empty
let favMovie = null; // When it is needed even when empty

🎭 Dynamic typing

JS is a dynamic language i.e., the type of the variable can change during runtime.

let data = 42;      // data is a Number
data = "Forty-two"; // data is now a String
data = true;        // data is now a Boolean

🧩 Reference Types

Type	description	Example
Object	A collection of properties	{ name: "John", age: 30 }
Array	A list of values	[1,2,3]
Function	A block of code

🔀 Type conversion

Explicitly convert varaible from one datatype to another.
Eg: String -> Number, Boolean -> String

typeof keyword

typeof keyword is used to check the data type of a variable

let data = 10;
console.log(typeof data); //Number

JS has a bunch of built-in ways to convert types. Think of them in 3 buckets: string, number, boolean

Convert to string

String(123) // "123"
(true).toString // "true"

Convert to Number

Number("123") // 123
praseInt("456abc") // 456
**NOTE**
Number("123go") // NaN

Convert to Boolean

Boolean(0) // false
Boolean("Hello") // true

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