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backend/node_modules/date-fns/differenceInYears/index.js

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+"use strict";
+
+var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault").default;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = differenceInYears;
+var _index = _interopRequireDefault(require("../toDate/index.js"));
+var _index2 = _interopRequireDefault(require("../differenceInCalendarYears/index.js"));
+var _index3 = _interopRequireDefault(require("../compareAsc/index.js"));
+var _index4 = _interopRequireDefault(require("../_lib/requiredArgs/index.js"));
+/**
+ * @name differenceInYears
+ * @category Year Helpers
+ * @summary Get the number of full years between the given dates.
+ *
+ * @description
+ * Get the number of full years between the given dates.
+ *
+ * @param {Date|Number} dateLeft - the later date
+ * @param {Date|Number} dateRight - the earlier date
+ * @returns {Number} the number of full years
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // How many full years are between 31 December 2013 and 11 February 2015?
+ * const result = differenceInYears(new Date(2015, 1, 11), new Date(2013, 11, 31))
+ * //=> 1
+ */
+function differenceInYears(dirtyDateLeft, dirtyDateRight) {
+  (0, _index4.default)(2, arguments);
+  var dateLeft = (0, _index.default)(dirtyDateLeft);
+  var dateRight = (0, _index.default)(dirtyDateRight);
+  var sign = (0, _index3.default)(dateLeft, dateRight);
+  var difference = Math.abs((0, _index2.default)(dateLeft, dateRight));
+
+  // Set both dates to a valid leap year for accurate comparison when dealing
+  // with leap days
+  dateLeft.setFullYear(1584);
+  dateRight.setFullYear(1584);
+
+  // Math.abs(diff in full years - diff in calendar years) === 1 if last calendar year is not full
+  // If so, result must be decreased by 1 in absolute value
+  var isLastYearNotFull = (0, _index3.default)(dateLeft, dateRight) === -sign;
+  var result = sign * (difference - Number(isLastYearNotFull));
+  // Prevent negative zero
+  return result === 0 ? 0 : result;
+}
+module.exports = exports.default;