Data Types in JavaScript
Every value in JavaScript has a data type. Understanding types is essential for writing correct and predictable code.
JavaScript has two main categories: primitive types (immutable basic values) and objects (complex, mutable data).
Primitive Types
There are seven primitive data types:
- String – text values
- Number – integers and floating-point numbers
- Boolean – true or false
- Undefined – variable declared but not assigned
- Null – intentional absence of value
- Symbol – unique identifiers (ES6)
- BigInt – arbitrary-precision integers (ES2020)
String
Number
JavaScript has one number type for both integers and floats.
Boolean
Undefined and Null
Symbol and BigInt
Objects
Everything else (arrays, functions, dates, etc.) is an object.
Checking Types with typeof
Quick Quiz
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