node.js - How to resolve these promise chaining?

Question

I am trying to write 2 routes for my node app. 1 route is to return single item and 1 route is for array list.

The routes are like these.

router
  .route("/:income_id")
  .get((req, res) => {
      Income.findById(req.params.income_id)
        .populate("services.service_id")
        .then((income) => {
          return filterIncomeFunc(income);
        })
        .then((result) => {
          return res.status(200).json(result);
        })
        .catch(function (error) {
          res.status(404).json({ msg: "Income not Found" });
        });
  });


 router
      .route("/")
      .get((req, res) => {
          Income.find({})
            .populate("services.service_id")
            .then((income) => { 
             //problem here
              return filterArrayIncome(income);
            })
            .then((result) => {
             console.log('======================');
             console.log(result);
             console.log('======================');
              return res.status(200).json(result);
            })
            .catch(function (error) {
              res.status(404).json({ msg: "Income not Found" });
            });
      });

Since I need to filter 2 of these i write 2 helper array named filterArrayIncome & filterIncomeFunc

I code works for single item but the array function is not working,

Here are my code for filtering

const filterIncomeFunc = (income) => {
  return new Promise((resolve, reject) => {
    let filteredIncome = {};
    filteredIncome.services = income.services.map((service) => {
      return {
        service_name: service.service_id.service_name,
        price: service.price,
      };
    });
    filteredIncome.total_amount = income.total_amount;
    resolve(filteredIncome);
  });
};

const filterArrayIncome = (incomeArray) => {
  return new Promise((resolve, reject) => {
    let filteredIncome = incomeArray.map((eachIncome) => {
     return filterIncomeFunc(eachIncome);
    });
    resolve(filteredIncome);
  });
};

Since i want dry code i am using filterIncomeFunc inside the filterArrayIncome

Inside the filterArrayIncome the console.log result is like this.

======================
[
  Promise {
    {
      services: [Array],
      total_amount: 18000
    }
  },
  Promise {
    {
      
      services: [Array],
      total_amount: 18000
    }
  },
]
======================

Y these are returning promises. I already resolve inside the filterArrayIncome func

question from:https://stackoverflow.com/questions/65889739/how-to-resolve-these-promise-chaining

Answer 1

You can use non-promises in promise chains.

Promise.resolve('a').then(() => 'b');

resolves to "b";

Your filter functions don't need to return promises, just have them return the values.

It makes no sense for them to return promises because they have everything they need to operate synchronously anyway.