composite property of a
KeyframeEffect resolves how an element’s animation impacts its underlying property values.
To understand these values, take the example of a
keyframeEffect value of
blur(2) working on an underlying property value of
replace- The keyframeEffect overrides the underlying value it is combined with:
add- The keyframeEffect is added to the underlying value with which it is combined (aka additive):
accumulate- The keyframeEffect is accumulated on to the underlying value:
Read more on MDN
I recommend reading web.dev’s article on web-animations.