Promises for cleaner async in Node.js - Mini Project: Build & Apply

Promises for cleaner async

📖 Scenario: You are building a small Node.js app that fetches user data and their posts from a server. Instead of using nested callbacks, you want to use Promises to keep your code clean and easy to read.

🎯 Goal: Build a simple Node.js script that uses Promises to fetch user data and posts asynchronously, then logs the combined result.

📋 What You'll Learn

Create a function that returns a Promise resolving user data

Create a function that returns a Promise resolving posts data

Use a configuration variable to simulate a delay time

Chain Promises to fetch user data first, then posts

Log the combined user and posts data after both Promises resolve

💡 Why This Matters

🌍 Real World

Using Promises is common in Node.js apps to handle asynchronous tasks like fetching data from APIs or databases without blocking the program.

💼 Career

Understanding Promises is essential for backend developers working with Node.js to write clean, maintainable asynchronous code.

1

Create user data fetch function

Create a function called fetchUser that returns a Promise resolving to the object { id: 1, name: 'Alice' } after a delay of 100 milliseconds.

Node.js

# Your code here

Need a hint?

Use new Promise and setTimeout to simulate async fetching.

2

Add delay configuration variable

Create a constant called delay and set it to 150 to use as the delay time for fetching posts.

Node.js

function fetchUser() {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve({ id: 1, name: 'Alice' });
        }, 100);
    });
}

# Your code here

Need a hint?

Use const delay = 150; to set the delay time.

3

Create posts data fetch function using delay

Create a function called fetchPosts that returns a Promise resolving to the array [{ id: 101, title: 'Post 1' }, { id: 102, title: 'Post 2' }] after a delay using the delay constant.

Node.js

function fetchUser() {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve({ id: 1, name: 'Alice' });
        }, 100);
    });
}

const delay = 150;

# Your code here

Need a hint?

Use the delay constant inside setTimeout for the posts fetch delay.

4

Chain Promises and log combined data

Use fetchUser() and chain it with fetchPosts() using .then(). Inside the second .then(), log an object with keys user and posts containing the resolved data.

Node.js

function fetchUser() {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve({ id: 1, name: 'Alice' });
        }, 100);
    });
}

const delay = 150;

function fetchPosts() {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve([
                { id: 101, title: 'Post 1' },
                { id: 102, title: 'Post 2' }
            ]);
        }, delay);
    });
}

# Your code here

Need a hint?

Chain fetchUser() and fetchPosts() with .then() and combine results in an object.