Data types in JavaScript
JavaScript has two main data types: primitives and objects. Let's examine each of them.
Primitive Types
Primitives are basic data types. Their value is immutable, and they're passed by value.
List of Primitives
NumberStringBooleanNullUndefinedSymbolBigInt
Important:
Primitives are immutable. For example, string methods don't change the string itself, but return a new one.
Objects
Objects are collections of data and functionality. They're passed by reference.
Examples of Objects
- Object — basic object.
- Array — ordered data collection.
- Function — object representing executable code.
- Date — object for working with dates.
- RegExp — object for working with regular expressions.
Examples of Creating Objects
javascript
// Regular object
const obj = { name: "John", age: 30 };
// Array
const arr = [1, 2, 3];
// Function
function greet() {
console.log("Hello!");
}typeof Examples
javascript
// typeof examples
console.log(typeof obj); // "object"
console.log(typeof arr); // "object"
console.log(typeof greet); // "function"
console.log(typeof null); // "object" (JS peculiarity)
console.log(typeof undefined); // "undefined"
console.log(typeof 42); // "number"
console.log(typeof "Hello"); // "string"
console.log(typeof Symbol("id")); // "symbol"
console.log(typeof 123n); // "bigint"typeof null Peculiarity:
To check data type use typeof. Remember that typeof null returns "object" — this is a historical bug in JavaScript.
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