JavaScript Data Types
JavaScript Data Types
JavaScript has two categories of data types:
✅ 1. Primitive Data Types
Primitive types are simple, immutable (cannot be changed), and stored directly in memory.
| Data Type | Example | Description |
|---|---|---|
String |
"Hello" |
Text data |
Number |
10, 10.5 |
Numeric values (integer + float) |
BigInt |
123n |
Very large numbers |
Boolean |
true / false |
Logical values |
Undefined |
let a; |
Variable declared but not assigned |
Null |
let a = null; |
Empty or intentionally no value |
Symbol |
Symbol("id") |
Unique and immutable value |
Examples:
✅ 2. Non-Primitive (Reference) Types
These are objects and stored by reference.
| Type | Example |
|---|---|
| Object | {name:"John", age:30} |
| Array | ["apple", "banana"] |
| Function | function hello(){...} |
Example:
📌 Type Checking Using typeof
⚠️ Note:
typeof nullreturns"object"— this is a known JavaScript mistake from early versions.
🧠 Special Notes
-
Strings can use
" ",' 'or
-
JavaScript Numbers are always floating-point:
🚀 Summary Table
| Category | Data Types |
|---|---|
| Primitive | String, Number, BigInt, Boolean, Undefined, Null, Symbol |
| Non-Primitive | Object, Array, Function |
