editroute_4.js

async function updateCompletedStudents(courseId, student, res) {

      /*
       * Substract -1 from @continuingStudents on system
       */
      
      try {
       
          //Get current system data
          let system  = await System.find({ 'systemId': SYSTEM_ID }).exec();
        
          //Substract -1 from continuingStudents
          system[0].continuingStudents -=1;

          try {
            
              //Update new system status
              await System.updateOne({ 'systemId': SYSTEM_ID }, system[0], { upsert: true }).exec();

          } catch (error) {
              console.log(error);

              res.status(Errors.DATABASE.DOC_UPDATE_OP_FAILED.CODE).send({
                  detail: Errors.FATAL_ERROR_MESSAGE
              });
          }
      } catch (error) {
        
          res.status(Errors.DATABASE.DOC_READ_OP_FAILED.CODE).send({
              detail: Errors.FATAL_ERROR_MESSAGE
          });
      }
  }