Function normalizeDuration

packages/runtime-dom/src/components/Transition.ts:300–311

(
  duration: TransitionProps['duration'],
)

}

function normalizeDuration(
  duration: TransitionProps['duration'],
): [number, number] | null {
  if (duration == null) {
    return null
  } else if (isObject(duration)) {
    return [NumberOf(duration.enter), NumberOf(duration.leave)]
  } else {
    const n = NumberOf(duration)
    return [n, n]
  }
}

function NumberOf(val: unknown): number {
  const res = toNumber(val)