错误：'未处理的 Promise 拒绝：TypeError：无法读取未定义的属性

Question

Getting this error when run ng test.

TypeError: Cannot read properties of undefined (reading 'id')

  this.slotSvc.getFiscalWeek(startDate, 1)
      .then(function (data) {
          const inductionYear = (data[0].id).split('-')[1];
          const shopId = slot.shop.id;
          const ohLines = [];
          this.slotSvc.getOlLinesForShop(shopId, inductionYear)
              .subscribe(function (d) {
                  _.each(d, function (dataOL) {
                      let slotLineType;
                      if (slot.linetype) {
                          slotLineType = slot.linetype;
                      } else {
                          slotLineType = slot.assignedAssetInfo.lineTypes[0];
                      }
                      if (dataOL.lineTypes[0] === slotLineType && dataOL.name.includes(slot.assetType)) {
                          const olJson = { 'id': dataOL.id, 'displayName': dataOL.displayName };
                          ohLines.push(olJson);
                      }
                  }.bind(this));

Answer 1

Seems like you are accessing id props from data that does not exists. Try to monitor data params and log data if it contains id prop or not.

Answer 2

you can do like this const inductionYear = (data[0]?.id).split('-')[1];

after putting question mark it will not give any undefined error.