You're attempting to define ease with a string and receiving this error.

animate(
  element,
  { opacity: 1 },
  { ease: "pow2" }
)

Solution

By defining ease as a string, you're trying to use one of Motion's in-built easing functions. Valid strings are:

• "linear"

• "easeIn"

• "easeInOut"

• "easeOut"

• "circIn"

• "circInOut"

• "circOut"

• "backIn"

• "backInOut"

• "backOut"

• "anticipate"

Alternatively, you can set ease to any JavaScript function that receives and returns a progress value.

const pow2 = p => p * p

animate(
  element,
  { opacity: 1 },
  { ease: pow2 }
)