JavaScript Simple Projects beginners - Online Stopwatch Full Screen

Last Updated: 2023-03-25 15:12:47

JavaScript Simple Projects Beginners Online Stopwatch Full Screen

JavaScript is a powerful language that's widely used for creating interactive web applications. If you're a beginner, it can be daunting to learn JavaScript, but there are many simple projects that you can start with to build your skills. One of these projects is creating an online stopwatch that displays in full screen.

In this tutorial, we'll guide you through the process of creating an online stopwatch in JavaScript that takes up the entire screen. The stopwatch will have start, stop, and reset buttons, and it will display the elapsed time in seconds, minutes, and hours.



What is Online Stopwatch Full Screen?

Online Stopwatch Full Screen is a web application that functions as a stopwatch timer and takes up the entire screen of the user's device. It's a simple project that can be created using HTML, CSS, and JavaScript, and is ideal for beginners who want to learn the basics of web development.

The main purpose of an online stopwatch is to measure elapsed time accurately. By creating a stopwatch that takes up the entire screen, users can easily keep track of their time without any distractions. This is especially useful for people who need to time themselves for specific tasks or activities, such as athletes, musicians, or professionals who need to manage their time effectively.

In addition, an online stopwatch that takes up the entire screen can be a great learning tool for people who are just starting to learn about web development. By building this simple project, beginners can gain a better understanding of how HTML, CSS, and JavaScript work together to create interactive web applications.

If you are a beginner and want to learn javascript from basic, please check out our other JavaScript Simple Projects With Source Code

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Design Online Stopwatch Full Screen in HTML CSS

First, let's create the HTML markup for the stopwatch. We'll create a container div with an id of "stopwatch" and add a timer element inside it. We'll also add three buttons for start, stop, and reset.

< div id="stopwatch">
  < timer>00:00:00< /timer>
  < button id="start-btn">Start< /button>
  < button id="stop-btn">Stop< /button>
  < button id="reset-btn">Reset< /button>
< /div>

Next, let's add some basic styles to our stopwatch using CSS. We'll make the container div take up the full screen by setting its height and width to 100vh and 100vw, respectively. We'll also center the timer element and make it larger using font-size.

#stopwatch {
  height: 100vh;
  width: 100vw;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;

timer {
  font-size: 10rem;
  text-align: center;



JavaScript Simple Project Stopwatch Code Example

Now, let's add some JavaScript code to make the stopwatch functional. We'll start by creating variables to keep track of the timer and the start time.

const timerEl = document.querySelector('timer');
let startTime;
let elapsedTime = 0;
let timerInterval;

Next, we'll create functions for starting, stopping, and resetting the stopwatch.

function startTimer() {
  startTime = - elapsedTime;
  timerInterval = setInterval(updateTimer, 10);

function stopTimer() {

function resetTimer() {
  elapsedTime = 0;



The startTimer() function sets the startTime to the current time minus the elapsed time, then starts a timerInterval that updates the timer every 10 milliseconds using the updateTimer() function.

The stopTimer() function stops the timerInterval.

The resetTimer() function stops the timerInterval, resets the elapsedTime to 0, and updates the timer.

Next, let's create the updateTimer() function.

function updateTimer() {
  const timeElapsed = - startTime;
  const seconds = Math.floor((timeElapsed / 1000) % 60);
  const minutes = Math.floor((timeElapsed / 1000 / 60) % 60);
  const hours = Math.floor((timeElapsed / 1000 / 60 / 60) % 24);
  timerEl.textContent = `${hours.toString().padStart(2, '0')}:${minutes.toString().padStart(2, '0')}:${seconds.toString().padStart(2, '0')}`;

The updateTimer() function calculates the timeElapsed by subtracting the startTime from the current time. It then calculates the seconds, minutes, and hours by dividing the timeElapsed by 1000 to get the number of seconds, minutes, and hours. Finally, it updates the timer element with the elapsed time in the format HH:MM:SS.

Next, let's add event listeners to the buttons.

document.getElementById('start-btn').addEventListener('click', startTimer);
document.getElementById('stop-btn').addEventListener('click', stopTimer);
document.getElementById('reset-btn').addEventListener('click', resetTimer);



The event listeners call the startTimer(), stopTimer(), and resetTimer() functions when the corresponding button is clicked.

And there you have it! You've just created an online stopwatch in JavaScript that takes up the entire screen. This is a great project for beginners to help them learn the basics of HTML, CSS, and JavaScript. With this project, you can continue to build on your skills and create even more complex web applications.

How this javascript project will help a beginner?

  1. Introducing a practical project: It provides a practical project that beginners can easily follow along to create an online stopwatch with JavaScript. By working on this project, beginners can gain hands-on experience and learn the basics of HTML, CSS, and JavaScript.
  2. Breaking down the steps: The post breaks down the steps involved in creating the online stopwatch project into easy-to-follow instructions. This makes it easier for beginners to understand how each component of the project works and how they can use it to create similar projects in the future.
  3. Highlighting key concepts: The post also highlights key concepts such as event listeners, interval functions, and DOM manipulation. These concepts are essential to understanding how JavaScript works and how it can be used to create interactive web applications.
  4. Providing a working example: The post provides a working example of the online stopwatch project that beginners can test and experiment with. This allows them to see how the different components of the project work together to create a fully functioning web application.

Overall, this post can help beginners develop their skills in web development by providing a practical project, breaking down the steps involved, highlighting key concepts, and providing a working example to test and experiment with.


creating an online stopwatch with JavaScript is a simple yet practical project that can be a great learning tool for beginners in web development. By following the steps outlined in this post, beginners can gain hands-on experience and learn the basics of HTML, CSS, and JavaScript while creating a fully functioning web application.



The project involves using event listeners, interval functions, and DOM manipulation to create a timer that accurately measures elapsed time. By creating an online stopwatch that takes up the entire screen, users can easily keep track of their time without any distractions, making it a useful tool for athletes, musicians, and professionals who need to manage their time effectively.

Still you face problems, feel free to contact with me, I will try my best to help you.