index.js 2.0 KB

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  1. "use strict";
  2. var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault").default;
  3. Object.defineProperty(exports, "__esModule", {
  4. value: true
  5. });
  6. exports.default = differenceInYears;
  7. var _index = _interopRequireDefault(require("../toDate/index.js"));
  8. var _index2 = _interopRequireDefault(require("../differenceInCalendarYears/index.js"));
  9. var _index3 = _interopRequireDefault(require("../compareAsc/index.js"));
  10. var _index4 = _interopRequireDefault(require("../_lib/requiredArgs/index.js"));
  11. /**
  12. * @name differenceInYears
  13. * @category Year Helpers
  14. * @summary Get the number of full years between the given dates.
  15. *
  16. * @description
  17. * Get the number of full years between the given dates.
  18. *
  19. * @param {Date|Number} dateLeft - the later date
  20. * @param {Date|Number} dateRight - the earlier date
  21. * @returns {Number} the number of full years
  22. * @throws {TypeError} 2 arguments required
  23. *
  24. * @example
  25. * // How many full years are between 31 December 2013 and 11 February 2015?
  26. * const result = differenceInYears(new Date(2015, 1, 11), new Date(2013, 11, 31))
  27. * //=> 1
  28. */
  29. function differenceInYears(dirtyDateLeft, dirtyDateRight) {
  30. (0, _index4.default)(2, arguments);
  31. var dateLeft = (0, _index.default)(dirtyDateLeft);
  32. var dateRight = (0, _index.default)(dirtyDateRight);
  33. var sign = (0, _index3.default)(dateLeft, dateRight);
  34. var difference = Math.abs((0, _index2.default)(dateLeft, dateRight));
  35. // Set both dates to a valid leap year for accurate comparison when dealing
  36. // with leap days
  37. dateLeft.setFullYear(1584);
  38. dateRight.setFullYear(1584);
  39. // Math.abs(diff in full years - diff in calendar years) === 1 if last calendar year is not full
  40. // If so, result must be decreased by 1 in absolute value
  41. var isLastYearNotFull = (0, _index3.default)(dateLeft, dateRight) === -sign;
  42. var result = sign * (difference - Number(isLastYearNotFull));
  43. // Prevent negative zero
  44. return result === 0 ? 0 : result;
  45. }
  46. module.exports = exports.default;