Data types in Java Script

What are Data Types?
Data types in JavaScript define the kind of value a variable can hold. They tell the JavaScript engine how to store and handle data.

Types of Data Types in JavaScript

JavaScript has 2 main categories:

1. Primitive Data Types (Basic Types)

These store single values and are immutable.

✔ List of Primitive Types:

1. Number
   let x = 10;
   let y = 3.14;

2. String
   let name = "John";
   let city = 'Chennai';
   Template literals:
   let msg = Hello ${name};
   Strings are immutable

3. Boolean
   Logical values:
   let isActive = true;
   let isDone = false;
   Used in:
   Conditions
   Comparisons

4. Undefined
   A variable declared but not assigned:
   let x;
   console.log(x); // undefined

5. Null
   Represents intentional absence of value:
   let data = null;
   Difference:
   undefined → no value assigned
   null → empty on purpose

6. BigInt
   For very large numbers:
   let big = 123456789012345678901234567890n;
   Used when numbers exceed safe limit (Number.MAX_SAFE_INTEGER)

7. Symbol
   Creates unique identifiers:
   let id1 = Symbol("id");
   let id2 = Symbol("id");
   console.log(id1 === id2); // false
   Always unique

What is Mutable and Immutable?

• Mutable
  A mutable object can be changed after it is created.
  You can modify:
  Its values
  Its properties

• Immutable
  An immutable value cannot be changed after creation.
  If you try to change it, you actually create a new value, not modify the original.

*Mutable in JavaScript (Detailed)
In JavaScript, non-primitive types are mutable:
Objects
Arrays
Functions
Example: Object (Mutable)
`let person = {
name: "John"
};

person.name = "Alex"; // modifying existing object

console.log(person.name); // Alex

✔ The original object is changed`
Mutable = same memory location is modified.

*Immutable in JavaScript (Detailed)
Primitive types are immutable:
Number
String
Boolean
Null
Undefined
BigInt
Symbol
Example: String (Immutable)
`let str = "hello";

str[0] = "H"; // trying to change

console.log(str); // "hello"

No change happens`