Avoiding flash of unwanted animation on first render in React
While developing my personal website, I noticed that my mobile menu appeared for a split second and then moved out of the screen. My mobile menu is placed on the right side of the screen by using the following CSS:
To make the menu come into the screen smoothly, I used the following CSS:
By adding this transition in my initial CSS, the menu will be transformed to the right side of the screen but with a duration of 150ms, so this will be clearly visible when the page loads.
To avoid this behaviour, I had to find a way to only apply the transition once the React app is already mounted.
For this use case, I found a custom
useIsMounted hook useful.
Then in my component, I can easily import this hook and use it:
My CSS then becomes this:
And that’s it! No more unwanted animations on page load. This will also help to increase your Cumulative Layout Shift (https://web.dev/cls) if you were encountering the same thing as I was, because your layout will not shift anymore, so it’s a win-win! You can see the end result here: https://thomasledoux.be (I use Tailwind on my site, so the example code is not exactly the same).