JavaScript Data Types - JavaScript Tutorial

Primitive Data Types

JavaScript has several primitive data types that represent simple values.

1. Number

The number data type represents both integer and floating-point numbers.

let age = 25;  // Integer
let price = 19.99;  // Floating-point
console.log(typeof age);  // Output: "number"
console.log(typeof price);  // Output: "number"

JavaScript
​x
 
let age = 25;  // Integerlet price = 19.99;  // Floating-pointconsole.log(typeof age);  // Output: "number"console.log(typeof price);  // Output: "number"

2. String

The string data type is used to represent text. Strings are enclosed in single quotes ('), double quotes ("), or backticks (`).

let name = "John";
let greeting = 'Hello, World!';
let template = `My name is ${name}`;
console.log(typeof name);  // Output: "string"
console.log(typeof greeting);  // Output: "string"
console.log(template);  // Output: "My name is John"

JavaScript
 
let name = "John";let greeting = 'Hello, World!';let template = `My name is ${name}`;console.log(typeof name);  // Output: "string"console.log(typeof greeting);  // Output: "string"console.log(template);  // Output: "My name is John"

3. Boolean

The boolean data type represents a logical value: true or false.

let isJavaScriptFun = true;
let isItRaining = false;
console.log(typeof isJavaScriptFun);  // Output: "boolean"
console.log(typeof isItRaining);  // Output: "boolean"

JavaScript
 
let isJavaScriptFun = true;let isItRaining = false;console.log(typeof isJavaScriptFun);  // Output: "boolean"console.log(typeof isItRaining);  // Output: "boolean"

4. Undefined

A variable that has been declared but not assigned a value is of type undefined.

let uninitialized;
console.log(typeof uninitialized);  // Output: "undefined"

JavaScript
 
let uninitialized;console.log(typeof uninitialized);  // Output: "undefined"

5. Null

The null data type represents an intentional absence of any object value. It is treated as an object type, but this is actually a bug in JavaScript.

let emptyValue = null;
console.log(typeof emptyValue);  // Output: "object"

JavaScript
 
let emptyValue = null;console.log(typeof emptyValue);  // Output: "object"

6. Symbol

The symbol data type is used to create unique identifiers for objects.

let uniqueId = Symbol("id");
console.log(typeof uniqueId);  // Output: "symbol"

JavaScript
 
let uniqueId = Symbol("id");console.log(typeof uniqueId);  // Output: "symbol"

Complex Data Type

JavaScript also has a complex data type known as Object.

Object

Objects are collections of key-value pairs. They can store multiple values as properties.

let person = {
    firstName: "John",
    lastName: "Doe",
    age: 30,
    isEmployed: true
};
console.log(typeof person);  // Output: "object"
console.log(person.firstName);  // Output: "John"

JavaScript
 
let person = {    firstName: "John",    lastName: "Doe",    age: 30,    isEmployed: true};console.log(typeof person);  // Output: "object"console.log(person.firstName);  // Output: "John"

JavaScript Data Types Example Code

Explanation of Code:

Number: Declares a variable age with a numeric value.
String: Declares a variable name with a string value.
Boolean: Declares a variable isStudent with a boolean value.
Undefined: Declares a variable city without assigning a value.
Null: Declares a variable car with a null value.
Symbol: Declares a variable sym with a unique symbol.
Object: Declares a variable person with properties.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>JavaScript Data Types Example</title>
</head>
<body>
    <script>
        // Number
        let age = 25;
        console.log("Age:", age);

        // String
        let name = "Jane";
        console.log("Name:", name);

        // Boolean
        let isStudent = true;
        console.log("Is student:", isStudent);

        // Undefined
        let city;
        console.log("City:", city);

        // Null
        let car = null;
        console.log("Car:", car);

        // Symbol
        let sym = Symbol("unique");
        console.log("Symbol:", sym);

        // Object
        let person = {
            firstName: "Jane",
            lastName: "Doe",
            age: 25
        };
        console.log("Person:", person);
    </script>
</body>
</html>

HTML
 
<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <meta name="viewport" content="width=device-width, initial-scale=1.0">    <title>JavaScript Data Types Example</title></head><body>    <script>        // Number        let age = 25;        console.log("Age:", age);​        // String        let name = "Jane";        console.log("Name:", name);​        // Boolean        let isStudent = true;        console.log("Is student:", isStudent);​        // Undefined        let city;        console.log("City:", city);​        // Null        let car = null;        console.log("Car:", car);​        // Symbol        let sym = Symbol("unique");        console.log("Symbol:", sym);​        // Object        let person = {            firstName: "Jane",            lastName: "Doe",            age: 25        };        console.log("Person:", person);    </script></body></html>