JavaScript Object Properties

Object properties are key-value pairs associated with an object. Each property has a key (also known as a name or identifier) and a corresponding value. Here are some common operations you can perform with object properties:

Accessing Object Properties

You can access object properties using dot notation or bracket notation.

const person = {
    firstName: "John",
    lastName: "Doe",
    age: 30
};

// Dot notation
console.log(person.firstName); // Output: John

// Bracket notation
console.log(person["lastName"]); // Output: Doe

Adding and Modifying Properties

You can add new properties to an object or modify existing ones by assigning values to them.

// Adding a new property
person.email = "john@example.com";

// Modifying an existing property
person.age = 31;

Deleting Properties

You can remove a property from an object using the delete keyword.

delete person.age;

Property Existence Check

You can check if a property exists in an object using the in operator or the hasOwnProperty() method.

// Using the "in" operator
if ("age" in person) {
    console.log("Age property exists.");
} else {
    console.log("Age property does not exist.");
}

// Using the hasOwnProperty() method
if (person.hasOwnProperty("age")) {
    console.log("Age property exists.");
} else {
    console.log("Age property does not exist.");
}

Enumerating Properties

You can loop through the properties of an object using a for...in loop.

for (let key in person) {
    console.log(key + ": " + person[key]);
}

Understanding how to work with object properties is essential for manipulating and managing objects effectively in JavaScript.