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JavaScript Course Operators in JavaScript

JavaScript Data Types

Last Updated : 08 Mar, 2025

In JavaScript, each value has a data type, defining its nature (e.g., Number, String, Boolean) and operations. Data types are categorized into Primitive (e.g., String, Number) and Non-Primitive (e.g., Objects, Arrays).

Primitive Data Type

1. Number

The Number data type in JavaScript includes both integers and floating-point numbers. Special values like Infinity, -Infinity, and NaN represent infinite values and computational errors, respectively.

JavaScript

let n1 = 2; console.log(n1)  let n2 = 1.3; console.log(n2)  let n3 = Infinity; console.log(n3)  let n4 = 'something here too' / 2; console.log(n4)

Output

2 1.3 Infinity NaN

2. String

A String in JavaScript is a series of characters that are surrounded by quotes. There are three types of quotes in JavaScript, which are.

JavaScript

let s1 = "Hello There"; console.log(s1);   let s2 = 'Single quotes work fine'; console.log(s2);   let s3 = `can embed ${s1}`; console.log(s3);

Output

Hello There Single quotes work fine can embed Hello There

There’s no difference between ‘single’ and “double” quotes in JavaScript. Backticks provide extra functionality as with their help of them we can embed variables inside them.

3. Boolean

The boolean type has only two values i.e. true and false.

JavaScript

let b1 = true; console.log(b1); let b2 = false; console.log(b2);

Output

true false

4. Null

The special null value does not belong to any of the default data types. It forms a separate type of its own which contains only the null value.

JavaScript

let age = null; console.log(age)

Output

null

The ‘null’ data type defines a special value that represents nothing, or empty value.

5. Undefined

A variable that has been declared but not initialized with a value is automatically assigned the undefined value. It means the variable exists, but it has no value assigned to it.

JavaScript

let a; console.log(a);

Output

undefined

6. Symbol (Introduced in ES6)

Symbols, introduced in ES6, are unique and immutable primitive values used as identifiers for object properties. They help create unique keys in objects, preventing conflicts with other properties.

JavaScript

let s1 = Symbol("Geeks"); let s2 = Symbol("Geeks"); console.log(s1 == s2);

Output

false

7. BigInt (Introduced in ES2020)

BigInt is a built-in object that provides a way to represent whole numbers greater than 2⁵³. The largest number that JavaScript can reliably represent with the Number primitive is 2⁵³, which is represented by the MAX_SAFE_INTEGER constant.

JavaScript

let b = BigInt("0b1010101001010101001111111111111111"); console.log(b);

Non-Primitive Data Types

The data types that are derived from primitive data types are known as non-primitive data types. It is also known as derived data types or reference data types.

1. Object

JavaScript objects are key-value pairs used to store data, created with {} or the new keyword. They are fundamental as nearly everything in JavaScript is an object.

JavaScript

let gfg = { type: "Company", location: "Noida" } console.log(gfg.type)

Output

Company

2. Arrays

An Array is a special kind of object used to store an ordered collection of values, which can be of any data type.

JavaScript

let a1 = [1, 2, 3, 4, 5]; console.log(a1); let a2 = [1, "two", { name: "Object" }, [3, 4, 5]]; console.log(a2);

Output

[ 1, 2, 3, 4, 5 ] [ 1, 'two', { name: 'Object' }, [ 3, 4, 5 ] ]

3. Function

A function in JavaScript is a block of reusable code designed to perform a specific task when called.

JavaScript

// Defining a function to greet a user function greet(name) { return "Hello, " + name + "!"; } // Calling the function console.log(greet("Ajay"));

Output

Hello, Ajay!

4. Date Object

The Date object in JavaScript is used to work with dates and times, allowing for date creation, manipulation, and formatting.

JavaScript

// Creating a new Date object for the current date and time let currentDate = new Date(); // Displaying the current date and time console.log(currentDate);

Output

2025-03-08T06:23:33.202Z

5. Regular Expression

A RegExp (Regular Expression) in JavaScript is an object used to define search patterns for matching text in strings.

JavaScript

// Creating a regular expression to match the word "hello" let pattern = /hello/; // Testing the pattern against a string let result = pattern.test("Hello, world!"); // Returns true because "Hello" matches the pattern console.log(result);

Output

false

Interesting Facts about Data Types

1. Dynamically Typed : JavaScript Variables are not bound to a specific data type. Mainly data type is stored with value (not with variable name) and is decided & checked at run time.

JavaScript

let x = 42; console.log(x) x = "hello"; console.log(x) x = [1, 2, 3] console.log(x)

Output

42 hello [ 1, 2, 3 ]

2. Everything is an Object (Sort of): In JavaScript, Functions are objects, arrays are objects, and even primitive values can behave like objects temporarily when you try to access properties on them.

JavaScript

let s = "hello"; console.log(s.length);    // Example with a number let x = 42; console.log(x.toString());   // Example with a boolean let y = true; console.log(y.toString());  /* Internal Working of primitives    to be treeated as objects     // Temporary wrapper object let temp = new String("hello");   console.log(temp.length); // 5  // The wrapper is discarded after use temp = null; */

Output

5 42 true

3. NaN is not equal to itself: NaN Stands for “Not-a-Number”, It is used to represent a computational error. NaN is technically of type number.

JavaScript

console.log(typeof NaN); console.log(NaN === NaN);

Output

number false

4. A Symbol is Never Equal to Another One : Symbol is a unique and immutable data type often used for creating private properties and methods. Symbols are never equal to any other Symbol.

JavaScript

let s1 = Symbol("abc"); let s2 = Symbol("abc"); console.log(s1 === s2);

Output

false

5. Undefined and Null: undefined represents a variable that has been declared but not assigned, while null is an explicit assignment representing “no value”.

6. Integers are Floating are Numbers only. There is only one type number that covers both integers and floating point numbers.

JavaScript

let x = 42; // Integer let y = 42.5; // Floating-point console.log(typeof x); console.log(typeof y);

Output

number number

7. A character is also a string. There is no separate type for characters. A single character is also a string.

JavaScript

let s1 = "gfg"; // String let s2 = 'g'; // Character console.log(typeof s1); console.log(typeof s2);

Output

string string

JavaScript Course Operators in JavaScript

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