Promises for Asynchronous JavaScript

Promises are a fundamental part of asynchronous programming, providing a convient way to manage asynchronous operations.

In this guide, we'll delve into the ins and outs of promises, covering their syntax, usage, common patterns, and best practices.

1 Minute Video

Why Do We Need Promises?

Before the introduction of promises, handling asynchronous operations in JavaScript relied heavily on callback functions.

While callbacks are functional, they often lead to a phenomenon known as callback hell, where nested callbacks become difficult to manage and understand.

Callback Demo

In this example, each callback function is nested inside the previous one, leading to a deeply nested and hard-to-read structure.

function getUserInfo (callback) {
    // callback 1: get user name
    getUserName(userId, (name) => {
        // callback 2: get user email
        getUserEmail(userId, (email) => {
            // callback 3: get user address
            getUserAddress(userId, (address) => {
                // callback 4: return user info
                callback({
                    name,
                    email,
                    address
                });
            });
        });
    });
}

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