Primitive and Reference value in JavaScript

In JavaScript, there are two types of data types: primitive and reference values.

Primitive values are immutable and are directly stored in memory. There are six primitive data types in JavaScript:

• String: represents a sequence of characters, enclosed in single or double quotes.

Example:

let name = 'John';

• Number: represents a numeric value, including integers and floating-point numbers.

Example:

let age = 25;

• Boolean: represents a logical value, either true or false.

Example:

let isStudent = true;

• Undefined: represents a variable that has been declared but has not been assigned a value.

Example:

let city;

• Null: represents a deliberate non-value or absence of any object value.

Example:

let car = null;

• Symbol: represents a unique identifier.

Example:

let id = Symbol('id');

Reference values are objects that are stored in memory and accessed by reference. There are three reference data types in JavaScript:

• Object: represents a collection of properties and methods.

Example:

let person = {
  name: 'John',
  age: 25,
  isStudent: true
};

• Array: represents a collection of elements, enclosed in square brackets.

Example:

let numbers = [1, 2, 3, 4, 5];

• Function: represents a reusable block of code that performs a specific task.

Example:

function greet(name) {
  console.log(`Hello, ${name}!`);
}

To differentiate between primitive and reference values, we can use the typeof operator. For example:

typeof 'John'; // "string"
typeof 25; // "number"
typeof true; // "boolean"
typeof undefined; // "undefined"
typeof null; // "object"
typeof Symbol('id'); // "symbol"
typeof { name: 'John', age: 25 }; // "object"
typeof [1, 2, 3, 4, 5]; // "object"
typeof function() {}; // "function"