setInterval and clearInterval in Node.js - Mini Project: Build & Apply

Using setInterval and clearInterval in Node.js

📖 Scenario: You are building a simple timer in Node.js that prints a message every second. You want to start the timer, count how many times the message has printed, and stop the timer after a certain number of prints.

🎯 Goal: Create a Node.js script that uses setInterval to print a message every second, counts the prints, and uses clearInterval to stop after 5 prints.

📋 What You'll Learn

Create a variable to count the number of prints

Create an interval using setInterval that prints a message every second

Stop the interval after 5 prints using clearInterval

💡 Why This Matters

🌍 Real World

Timers like this are used in real applications to perform tasks repeatedly, such as updating a clock, checking for new messages, or refreshing data.

💼 Career

Understanding how to use timers and control their lifecycle is important for backend and frontend developers to manage asynchronous tasks and improve user experience.

1

Create a counter variable

Create a variable called count and set it to 0.

Node.js

// Create a variable called count and set it to 0
// Your code here

Need a hint?

Use let count = 0; to create a variable that can change.

2

Create an interval to print a message every second

Create a variable called intervalId and assign it the result of setInterval. Inside setInterval, write a function that prints 'Hello every second' and increases count by 1. Set the interval time to 1000 milliseconds.

Node.js

let count = 0;
// Create intervalId using setInterval to print message and increase count every 1000 ms
// Your code here

Need a hint?

Use setInterval(() => { ... }, 1000) to run code every second.

3

Stop the interval after 5 prints

Inside the setInterval function, add an if statement that checks if count is equal to 5. If yes, call clearInterval(intervalId) to stop the interval.

Node.js

let count = 0;

const intervalId = setInterval(() => {
    console.log('Hello every second');
    count += 1;
    // Stop interval after 5 prints
    // Your code here
}, 1000);

Need a hint?

Use if (count === 5) { clearInterval(intervalId); } to stop the timer.

4

Add a final message after stopping the interval

After calling clearInterval(intervalId), add a line inside the if block that prints 'Timer stopped after 5 prints.'.

Node.js

let count = 0;

const intervalId = setInterval(() => {
    console.log('Hello every second');
    count += 1;
    if (count === 5) {
        clearInterval(intervalId);
        // Print final message
        // Your code here
    }
}, 1000);

Need a hint?

Use console.log('Timer stopped after 5 prints.'); inside the if block.