Function buildRootMargin

src/utils/buildRootMargin.ts:22–38

(
  scrollThreshold: number | string,
  inverse: boolean
)

 * For inverse mode the margin is applied to the top instead of the bottom.
 */
export function buildRootMargin(
  scrollThreshold: number | string,
  inverse: boolean
): string {
  const threshold = parseThreshold(scrollThreshold);

  let margin: string;
  if (threshold.unit === ThresholdUnits.Pixel) {
    margin = `${threshold.value}px`;
  } else {
    // threshold.value is already in percent (e.g. 80 for 0.8 input)
    const remaining = 100 - threshold.value;
    margin = `${remaining}%`;
  }

  return inverse ? `${margin} 0px 0px 0px` : `0px 0px ${margin} 0px`;
}