temp.js

 else if (Obj.diff == true) {
    // creating a promise to insert two transaction records
    let promise = new Promise(function(resolve, reject) {
      setTimeout(() => resolve("done!"), 1000);
    })
      .then((firstIteration, error) => {
        let firstMonthFromDate = Obj.monthFrom;
        let firstMonthToDate = Obj.monthTo;

        Transaction.create({
          fromDate: firstMonthFromDate,
          toDate: firstMonthToDate,
          reason: reason,
          typeOfLeave: typeOfLeave,
          year: year,
          totalDays: totalDays,
          fromDatePartOfDay: fromDatePartOfDay,
          toDatePartOfDay: toDatePartOfDay,
          description: description,
          flagged: flagged,
          flagDescription: flagDescription,
          employeeId: employeeId
        }).then(data => {
          LeaveStore.findAll({
            where: {
              employeeId: employeeId
            }
          }).then(leavestore => {
            Transaction.findAll({
              where: {
                employeeId: employeeId
              }
            }).then(gg => {
              let temp = gg[0].typeOfLeave;
              temp = temp.toLowerCase() + "Consumption";
              tempAcc = temp.toLowerCase() + "Accural";
              LeaveStore.update(
                {
                  [temp]: parseInt(leavestore[0][temp]) + parseInt(totalDays),
                  [tempAcc]:
                    parseInt(leavestore[0][tempAcc]) -
                    parseInt(leavestore[0][temp]),
                  netLeaveBalance:
                    parseInt(leavestore[0].netLeaveBalance) -
                    parseInt(totalDays)
                },
                {
                  where: {
                    employeeId: employeeId
                  }
                }
              );
              Transaction.update(
                {
                  balanceAfterTransaction:
                    parseInt(leavestore[0].netLeaveBalance) -
                    parseInt(totalDays)
                },
                {
                  where: {
                    employeeId: employeeId
                  }
                }
              );
              // .then(success => {
              //   res.jsonp({
              //     success: true,
              //     data: `Leave successfully applied`
              //   });
              // });
            });
          });
        });
        error => console.log(error, "error in firstIteration");
      })
      .finally(secondIteration => {
        let secondMonthFromDate = Obj.newMonthFrom;
        let secondMonthToDate = Obj.newMonthTo;
        Transaction.create({
          fromDate: secondMonthFromDate,
          toDate: secondMonthToDate,
          reason: reason,
          typeOfLeave: typeOfLeave,
          year: year,
          totalDays: totalDays,
          fromDatePartOfDay: fromDatePartOfDay,
          toDatePartOfDay: toDatePartOfDay,
          description: description,
          flagged: flagged,
          flagDescription: flagDescription,
          employeeId: employeeId
        }).then(data => {
          LeaveStore.findAll({
            where: {
              employeeId: employeeId
            }
          }).then(leavestore => {
            Transaction.findAll({
              where: {
                employeeId: employeeId
              }
            }).then(gg => {
              let temp = gg[0].typeOfLeave;
              temp = temp.toLowerCase() + "Consumption";
              tempAcc = temp.toLowerCase() + "Accural";
              LeaveStore.update(
                {
                  [temp]: parseInt(leavestore[0][temp]) + parseInt(totalDays),
                  [tempAcc]:
                    parseInt(leavestore[0][tempAcc]) -
                    parseInt(leavestore[0][temp]),
                  netLeaveBalance:
                    parseInt(leavestore[0].netLeaveBalance) -
                    parseInt(totalDays)
                },
                {
                  where: {
                    employeeId: employeeId
                  }
                }
              );
              Transaction.update(
                {
                  balanceAfterTransaction:
                    parseInt(leavestore[0].netLeaveBalance) -
                    parseInt(totalDays)
                },
                {
                  where: {
                    employeeId: employeeId
                  }
                }
              ).then(success => {
                res.jsonp({
                  success: true,
                  data: `Leave successfully applied`
                });
              });
            });
          });
        });
        error => console.log(error, "error in secondIteration");
      });
  }