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  1. "use strict";
  2. Object.defineProperty(exports, "__esModule", {
  3. value: true
  4. });
  5. exports.default = differenceInMonths;
  6. var _index = _interopRequireDefault(require("../toDate/index.js"));
  7. var _index2 = _interopRequireDefault(require("../differenceInCalendarMonths/index.js"));
  8. var _index3 = _interopRequireDefault(require("../compareAsc/index.js"));
  9. var _index4 = _interopRequireDefault(require("../_lib/requiredArgs/index.js"));
  10. function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
  11. /**
  12. * @name differenceInMonths
  13. * @category Month Helpers
  14. * @summary Get the number of full months between the given dates.
  15. *
  16. * @description
  17. * Get the number of full months between the given dates.
  18. *
  19. * ### v2.0.0 breaking changes:
  20. *
  21. * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
  22. *
  23. * @param {Date|Number} dateLeft - the later date
  24. * @param {Date|Number} dateRight - the earlier date
  25. * @returns {Number} the number of full months
  26. * @throws {TypeError} 2 arguments required
  27. *
  28. * @example
  29. * // How many full months are between 31 January 2014 and 1 September 2014?
  30. * var result = differenceInMonths(new Date(2014, 8, 1), new Date(2014, 0, 31))
  31. * //=> 7
  32. */
  33. function differenceInMonths(dirtyDateLeft, dirtyDateRight) {
  34. (0, _index4.default)(2, arguments);
  35. var dateLeft = (0, _index.default)(dirtyDateLeft);
  36. var dateRight = (0, _index.default)(dirtyDateRight);
  37. var sign = (0, _index3.default)(dateLeft, dateRight);
  38. var difference = Math.abs((0, _index2.default)(dateLeft, dateRight));
  39. dateLeft.setMonth(dateLeft.getMonth() - sign * difference); // Math.abs(diff in full months - diff in calendar months) === 1 if last calendar month is not full
  40. // If so, result must be decreased by 1 in absolute value
  41. var isLastMonthNotFull = (0, _index3.default)(dateLeft, dateRight) === -sign;
  42. var result = sign * (difference - isLastMonthNotFull); // Prevent negative zero
  43. return result === 0 ? 0 : result;
  44. }
  45. module.exports = exports.default;