How to Prevent Function Duplication on Every Page Load with JavaScript deviceready

Описание: Discover how to effectively manage JavaScript events and avoid firing them multiple times when switching HTML pages in your web application.
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This video is based on the question https://stackoverflow.com/q/67794426/ asked by the user 'Janssen Schembri' ( https://stackoverflow.com/u/15864864/ ) and on the answer https://stackoverflow.com/a/67795153/ provided by the user 'Rômulo Bourget Novas' ( https://stackoverflow.com/u/2379541/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Prevent Function Duplication on Every Page Load with JavaScript deviceready

Creating a seamless user experience is crucial in web applications, especially when dealing with features that rely on device state, such as battery level alerts. One common issue developers face is the unintended repetition of functions when navigating between HTML pages. In this guide, we'll discuss a specific problem related to the deviceready event and how to resolve it effectively.

The Problem: Repeated Alerts on Page Navigation

In the scenario described, a function is designed to alert the user when their battery level drops below 15%. However, this function keeps firing every time the user loads a new HTML page within the application, causing repetitive alerts—even if the battery level has not changed. This behavior occurs because the JavaScript code is re-executed each time a new page loads. Specifically, the deviceready event listener continues to trigger, leading to unwanted behavior.

Key Symptoms of the Issue:

Multiple alerts for low battery on navigating pages.

Redundant calls to the onBatteryStatus function, generating clutter in the console.

The Solution: Using Local Storage

To solve this issue, we can utilize the browser's localStorage feature. This allows us to keep record of whether the user has already been alerted about a low battery on the current session. By doing so, we can prevent the alert from being triggered multiple times unnecessarily.

Updated Code Implementation

Here’s how you can adjust your existing code to avoid firing alerts repeatedly:

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

Explanation of Key Changes:

Local Storage Check: Before alerting the user of a low battery, the function checks localStorage for the alerted key. If it doesn’t exist (indicating the user hasn’t been alerted during this session), the alert will display.

Setting and Removing the Alert: After the alert is shown, the function sets localStorage.alerted to true. When the battery level increases above 15%, the alerted key is removed, allowing the alert to show again if the battery drops low in the future.

Conclusion

By leveraging localStorage, you can maintain a smooth user experience while keeping your JavaScript functions from firing repeatedly across page loads. This approach not only enhances your application's usability but also helps you write cleaner and more efficient code.

With these changes, you can prevent multiple alerts—creating a better overall application for your users. If you have similar functionality in your apps, consider employing these strategies to enhance your user experience. Happy coding!