Promise chaining in Javascript - Mini Project: Build & Apply

Promise chaining

📖 Scenario: Imagine you are ordering a pizza online. First, you select the pizza, then you pay for it, and finally, you get a confirmation message. Each step happens one after the other.

🎯 Goal: You will create three functions that return promises for each step: selectPizza, payForPizza, and confirmOrder. Then, you will chain these promises together to show the full order process.

📋 What You'll Learn

Create a function called selectPizza that returns a promise resolving to the string 'Pizza selected'.

Create a function called payForPizza that takes a string and returns a promise resolving to 'Payment done'.

Create a function called confirmOrder that takes a string and returns a promise resolving to 'Order confirmed'.

Chain the three functions using .then() to run them one after another.

Print the final confirmation message.

💡 Why This Matters

🌍 Real World

Promise chaining is used in real life when you need to do tasks one after another that take time, like loading data from the internet or processing payments.

💼 Career

Understanding promise chaining is important for web developers to handle asynchronous operations smoothly, improving user experience and app reliability.

1

Create the selectPizza function

Write a function called selectPizza that returns a promise which resolves to the string 'Pizza selected'.

Javascript

// Your code here

Need a hint?

Use new Promise and call resolve with the string 'Pizza selected'.

2

Create the payForPizza function

Write a function called payForPizza that takes one parameter called message and returns a promise which resolves to the string 'Payment done'.

Javascript

function selectPizza() {
    return new Promise((resolve) => {
        resolve('Pizza selected');
    });
}

// Your code here

Need a hint?

The function takes message but you only need to resolve with 'Payment done'.

3

Create the confirmOrder function

Write a function called confirmOrder that takes one parameter called message and returns a promise which resolves to the string 'Order confirmed'.

Javascript

function selectPizza() {
    return new Promise((resolve) => {
        resolve('Pizza selected');
    });
}

function payForPizza(message) {
    return new Promise((resolve) => {
        resolve('Payment done');
    });
}

// Your code here

Need a hint?

Similar to the other functions, resolve with 'Order confirmed'.

4

Chain the promises and print the final message

Use selectPizza() and chain it with payForPizza and confirmOrder using .then(). Finally, print the result of confirmOrder using console.log.

Javascript

function selectPizza() {
    return new Promise((resolve) => {
        resolve('Pizza selected');
    });
}

function payForPizza(message) {
    return new Promise((resolve) => {
        resolve('Payment done');
    });
}

function confirmOrder(message) {
    return new Promise((resolve) => {
        resolve('Order confirmed');
    });
}

// Your code here

Need a hint?

Chain the functions with .then() and print the last result with console.log.