const filteredPrices = drug.map(item => {
    const errorCodes = drugPriceErrors;
    const pricePath = ['mailPrice.rejectMessage', 'retailPrice.rejectMessage'];

    _.forEach(pricePath, function (path)  {
      const rejectMsg = _.get(item, path);
      const hasCode = rejectMsg && rejectMsg.find(i => !!~errorCodes.indexOf(+i.settlementCode));
      hasCode && delete item[path.split('.').shift()];
    });

    return item;
  });

TypeError: drug.map is not a function