Variables and Datatypes in JavaScript

In JavaScript, understanding variables and data types is crucial for effective programming. This knowledge forms the foundation for managing data and controlling program behavior.

Aspect	Description
Variables	Containers for storing data values.
Declaration Keywords	– var: Function-scoped or globally-scoped. – let: Block-scoped and reassignable. – const: Block-scoped and immutable after assignment.

Data Types

Data Type	Description	Example
Number	Represents both integer and floating-point numbers.	let num = 42;
String	A sequence of characters enclosed in quotes.	let str = "Hello, World!";
Boolean	Represents a logical entity with two values: true or false.	let isActive = true;
Null	Represents the intentional absence of any value.	let emptyValue = null;
Undefined	Indicates that a variable has been declared but not assigned a value.	let notAssigned;
Symbol	A unique and immutable primitive value used as an identifier.	const sym = Symbol('description');
BigInt	Represents integers with arbitrary precision.	const bigIntValue = BigInt(12345678901234567890);
Object	A complex data type that can store collections of data.	const person = { name: "John", age: 30 };
Array	A special type of object used to store ordered collections.	const fruits = ["apple", "banana", "cherry"];
Function	Functions are also objects and can be treated as first-class citizens.	function greet() { return "Hello!"; }

Checking Data Types

Method	Description
typeof	Returns the type of a variable as a string.

Example Usage

javascriptconsole.log(typeof num); // "number"
console.log(typeof str); // "string"
console.log(typeof isActive); // "boolean"

This table provides a clear and organized overview of variables and data types in JavaScript, making it easy to reference key concepts at a glance!

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