What is an object?
Think of a user's profile card: it has a name, an email, an age. Or a product: price, stock, category. Each one is a handful of pieces of data that only make sense together. That, exactly, is an object.
An object groups related data into key: value pairs. If an array was a numbered row, an object is the card with labels:
const person = {
name: "Ana",
age: 30,
active: true,
};
Each pair (name: "Ana") is a property: the key is the label and the value,
its content. And you can ask that card anything you like.
Dot access
The most common form:
console.log(person.name); // "Ana"
console.log(person.age); // 30
Bracket access
Useful when the key is stored in a variable or has special characters (spaces, dashes) that dot notation won't accept:
const key = "age";
console.log(person[key]); // 30
console.log(person["name"]); // "Ana"
Adding and modifying properties
person.email = "ana@mail.com"; // adds
person.age = 31; // modifies
delete person.active; // deletes
⚠️ Classic trap: if you ask for a property that doesn't exist, JavaScript won't complain: it just hands you
undefined. No red errors, so double-check how you spell the key.
Examples
A book's card: creating it and reading it
const book = {
title: "Hopscotch",
author: "Cortázar",
pages: 600,
};
console.log(book.title); // "Hopscotch"
console.log(book["author"]); // "Cortázar"