Receiving promise from another module in NodeJS with data

Question

I am really new to promises in javascript so I really don't understand what I may be missing in my code. Basically my problem is that in my main program I am trying to iterate through a json array using async.forEachOf and inside that I am calling the DAO.processData and after completing the loop I want to send the response. If there is a better solution to this please do help.

Now here I am trying to access a value from another module that is returning a promise object along with a value. The promise returning module looks like below:

var dao = {}

dao.processData = function(data) {

  var finalPromise = new Promise(()=>{});

  async.waterfall([function1, function2, function3], someCallBackFunction);

  someCallBackFunction = function () {
    console.log('in some function');
    finalPromise = new Promise( (resolve,reject) => {
      resolve(data++);
    })

    return finalPromise;
  }

}

module.exports = dao

The module receiving the data looks like below.

const DAO = require('./myObject')

var myArray = [1, 2]

var jsonResponse = {}

someRouterFunction = function (req, res) {

  async.forEachOf(myArray, (number) => {
    Promise.resolve(DAO.processData(number)).then( prepareResponse )
  .catch ( e => { console.log(e) } );
  }, (err) => {
    res.json(jsonResponse);
  })
  
}

function prepareResponse (res) {
  jsonResponse = {
    'msg': res
  }
}

someRouterFunction();

With this code it returns cannot read propety 'then' of undefined. So I did the following in the someRouterFunction:

  Promise.resolve(DAO.processData(number)).then( prepareResponse );

This makes the call to the function but I am never able to access the returned value which is res here in the prepareResponse function.

Receiving promise from another module in NodeJS with data

0 Answers0