The 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 blur(3).
replaceThe keyframeEffect overrides the underlying value it is combined with: blur(2) replaces blur(3).
addThe keyframeEffect is added to the underlying value with which it is combined (aka additive): blur(2) blur(3).
accumulateThe keyframeEffect is accumulated on to the underlying value: blur(5).
KeyframeEffect objects