JavaScript Object Properties

JavaScript objects consist of properties and methods. Properties are key-value pairs where the key is a string and the value can be any data type. Understanding object properties is crucial for working effectively with objects in JavaScript.

1. Accessing Properties

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

Dot Notation

const person = {
    name: "Alice",
    age: 25
};

console.log(person.name); // Alice

            

Bracket Notation

const person = {
    name: "Alice",
    age: 25
};

console.log(person["age"]); // 25

            

Bracket notation is useful when the property name is dynamic or not a valid identifier.

2. Modifying Properties

You can modify properties using both dot notation and bracket notation in a similar way to accessing them.

Dot Notation

const person = {
    name: "Alice",
    age: 25
};

person.age = 26;
console.log(person.age); // 26

            

Bracket Notation

const person = {
    name: "Alice",
    age: 25
};

person["age"] = 26;
console.log(person["age"]); // 26

            

3. Adding Properties

New properties can be added to objects dynamically.

const person = {
    name: "Alice"
};

person.age = 25;
console.log(person.age); // 25

            

4. Deleting Properties

Properties can be removed from objects using the delete operator.

const person = {
    name: "Alice",
    age: 25
};

delete person.age;
console.log(person.age); // undefined

            

5. Property Attributes

JavaScript object properties have attributes like writable, enumerable, and configurable. You can view and modify these attributes using Object.getOwnPropertyDescriptor and Object.defineProperty.

Viewing Property Attributes

const person = {
    name: "Alice"
};

const descriptor = Object.getOwnPropertyDescriptor(person, "name");
console.log(descriptor);

            

Modifying Property Attributes

const person = {
    name: "Alice"
};

Object.defineProperty(person, "name", {
    writable: false
});

person.name = "Bob"; // This will not change the name property
console.log(person.name); // Alice