text: let benefit = {
      // 减免金额
      money: null
  }
  
  class Benefit {
      // 新增限制
      addBenefit(key) {
          benefit[key] = null
      }
  
      // 删除限制
      delBenefit(key) {
          delete benefit[key]
      }
  
      // 设置限制的一项值
      setBenefitValue(key, value) {
          benefit[key] = value
      }
  
      getBenefit() {
          let _output = {}
          for (let key in benefit) {
              if (benefit[key] !== null) _output[key] = benefit[key];
          }
          return _output
      }
  }
  
  module.exports = Benefit;