text: import { Q, M, D } from '../../constant';
  export default (function (o, c) {
    var proto = c.prototype;
  
    proto.quarter = function (quarter) {
      if (!this.$utils().u(quarter)) {
        return this.month(this.month() % 3 + (quarter - 1) * 3);
      }
  
      return Math.ceil((this.month() + 1) / 3);
    };
  
    var oldAdd = proto.add;
  
    proto.add = function (number, units) {
      number = Number(number); // eslint-disable-line no-param-reassign
  
      var unit = this.$utils().p(units);
  
      if (unit === Q) {
        return this.add(number * 3, M);
      }
  
      return oldAdd.bind(this)(number, units);
    };
  
    var oldStartOf = proto.startOf;
  
    proto.startOf = function (units, startOf) {
      var utils = this.$utils();
      var isStartOf = !utils.u(startOf) ? startOf : true;
      var unit = utils.p(units);
  
      if (unit === Q) {
        var quarter = this.quarter() - 1;
        return isStartOf ? this.month(quarter * 3).startOf(M).startOf(D) : this.month(quarter * 3 + 2).endOf(M).endOf(D);
      }
  
      return oldStartOf.bind(this)(units, startOf);
    };
  });