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` `(template literals):
JavaScript Numbers are always floating-point:
🚀 Summary Table
| Category | Data Types |
|---|---|
| Primitive | String, Number, BigInt, Boolean, Undefined, Null, Symbol |
| Non-Primitive | Object, Array, Function |
