从 Sequelize 返回值

Question

The below code is to get due amount by subtracting actual fee with amount paid. I get value returned as null instead of difference. WHen i add return for db.XXX.findOne, I get error as "Invalid value Promise". Please help me understand where i went wrong

let x=getDueAmount(1,200);

const getDueAmount = (id,amountpaid) => {
  let due;
  db.XXX.findOne({
    where:{id: id},
    attributes:['fees']
   }).then(feeDetail=>{
      due=feeDetail.fees-amountpaid;
       });
   return due;
}

Answer 1

Simply return from your promise (your Db call). In your code your returning the value of due prior to the result coming back from the db. Read up on promises and asynchronous javascript

let x=getDueAmount(1,200);

const getDueAmount = (id,amountpaid) => {
  return db.XXX.findOne({
    where:{id: id},
    attributes:['fees']
   }).then(feeDetail=>{
     return feeDetail.fees-amountpaid;
   });
}