Creating a Functional session timer in ReactJS with setInterval()

Learn how to effectively implement a session timer in ReactJS using hooks and `setInterval()`, avoiding common pitfalls like irregular counting and null outputs.
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This video is based on the question https://stackoverflow.com/q/68873826/ asked by the user 'Ruben99' ( https://stackoverflow.com/u/16609802/ ) and on the answer https://stackoverflow.com/a/68877478/ provided by the user 'Ruben99' ( https://stackoverflow.com/u/16609802/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Creating a Functional session timer in ReactJS with setInterval()

Building a session timer in ReactJS can be tricky, especially when you're trying to keep track of time on different pages. This post will guide you through the process of setting up a session timer using React hooks and the setInterval() function while highlighting potential pitfalls you've probably encountered.

Understanding the Problem

The challenge I faced was to create a timer that:

Starts at 00:00 when the user loads the Home page.

Increments every second.

Resets to 00:00 when the user navigates to a different page.

Some difficulties included:

Irregular counting and unexpected output.

Multiple timers running simultaneously and adding their outputs together.

Getting “null” outputs on the timer.

Steps to Create a Functional Timer

Let’s break down the solution into clear steps to ensure you set this up correctly.

1. Initialize State

First, initialize state to keep track of the timer count.

[[See Video to Reveal this Text or Code Snippet]]

2. Setup the Timer

You’ll use useEffect() to handle starting and clearing the timer:

[[See Video to Reveal this Text or Code Snippet]]

3. Calculate Time Format

To display the time correctly in minutes and seconds, calculate the values by using:

[[See Video to Reveal this Text or Code Snippet]]

Then, you can format it for display by padding with zeros:

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4. Ensure Proper Navigation Handling

Make sure that your button functions correctly change the page:

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5. Putting It All Together

Your completed component should look something like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these steps, you can successfully create a session timer in your ReactJS application that behaves predictably. This approach ensures that the timer starts and resets correctly while avoids common issues like multiple intervals firing at once. Happy coding!

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