date-fns/src/differenceInQuarters/index.ts


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import differenceInMonths from '../differenceInMonths/index'
import requiredArgs from '../_lib/requiredArgs/index'

/**
 * @name differenceInQuarters
 * @category Quarter Helpers
 * @summary Get the number of full quarters between the given dates.
 *
 * @description
 * Get the number of full quarters between the given dates.
 *
 * ### v2.0.0 breaking changes:
 *
 * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
 *
 * @param {Date|Number} dateLeft - the later date
 * @param {Date|Number} dateRight - the earlier date
 * @returns {Number} the number of full quarters
 * @throws {TypeError} 2 arguments required
 *
 * @example
 * // How many full quarters are between 31 December 2013 and 2 July 2014?
 * var result = differenceInQuarters(new Date(2014, 6, 2), new Date(2013, 11, 31))
 * //=> 2
 */
export default function differenceInQuarters(
  dirtyDateLeft: Date | number,
  dirtyDateRight: Date | number
): number {
  requiredArgs(2, arguments)

  const diff = differenceInMonths(dirtyDateLeft, dirtyDateRight) / 3
  return diff > 0 ? Math.floor(diff) : Math.ceil(diff)
}