Scrolling performance is crucial for a smooth user experience on websites. One common issue that can impact scrolling performance is the use of passive event listeners. If you've come across the "Does not use passive listeners to improve scrolling performance" warning in a Lighthouse report, don't worry, we've got you covered with some tips to address this issue.
Passive event listeners are a way to improve scrolling performance by telling the browser that the event listener will not prevent scrolling. This can be particularly useful when handling touch and wheel events. However, if passive event listeners are not used correctly, they can actually have a negative impact on performance.
To address the "Does not use passive listeners to improve scrolling performance" warning, you can start by identifying where in your codebase passive event listeners are being used incorrectly. This typically happens when event listeners are added without specifying the passive option.
To use passive event listeners correctly, you need to ensure that you explicitly set the passive option to true when adding event listeners that will not call preventDefault(). By doing this, you can help the browser optimize scrolling performance and avoid unnecessary delays.
In JavaScript, when adding an event listener, you can specify the passive option like this:
element.addEventListener("touchstart", handleTouchStart, { passive: true });By setting passive: true, you are telling the browser that the event listener will not prevent default behavior, allowing it to optimize scrolling performance. This simple adjustment can make a significant difference in how smoothly your website scrolls.
When optimizing scrolling performance, it's essential to pay attention to these seemingly small details, as they can have a considerable impact on the overall user experience. By addressing the "Does not use passive listeners to improve scrolling performance" warning, you are taking a proactive step towards creating a faster and more responsive website.
In conclusion, passive event listeners play a crucial role in optimizing scrolling performance on websites. By using them correctly and specifying the passive option where needed, you can help improve the overall user experience and address performance issues highlighted in Lighthouse reports. So, next time you encounter this warning, remember to check your code for incorrect usage of passive event listeners and make the necessary adjustments to enhance scrolling performance. Your users will thank you for it!