Getting "ReferenceError" error while performing multiple chaining of promise in nodejs application for neo4j import using cypher query

Question

I am writing nodejs application using neo4j js driver (and async utility module) to use a project's source js files' data to be imported in neo4j database.

There are 2 folders namely "State"and "City" and a single "country.js" file in my test project folder "testapp". The "country.js" file contains the name and id of the countries and the countryid is used as a parameter in the js files present in the folders "State"and "City".

-- snippet from country.js file

const countries= [
{ id: "1", label: "USA" }, 
{ id: "2", label: "Scotland" }
];
module.exports = countries;

The "State" folder has js files which has naming convention like this: (Country-1-statelist.js, Country-2-statelist.js and so on).

--Sample from js file present in "State" folder.

    const data = {"params":{"country_id":"1"},"items":
    [{"id":"1","label":"Alaska"},{"id":"2","label":"Alabama"}]
      module.exports = data;

Similarly, "City" folder has js files which has naming convention like this: (Country-1-state-1-list.js, Country-1-state-2-list.js and so on).

-- sample from a particular js file present in "City" folder

const data = 
  {"params":
   {"country_id":"1","state_id":"1"},

   "items":[
       {"id":"1","label":"New York"},
       {"id":"2","label":"Chicago"}
   ]
        }
 module.exports = data;

So,I am trying to add nodes with label Countries, States and Cities such that they would be imported without their relationship being unaltered. But I am getting error in nodejs while trying to use multiple chain promise to import it into my test db.

so, far I was able to import the data present in country.js and other js files from "State" folder. But while trying to do the same from js files of "City" folder, I am getting "ReferenceError: item is not defined" error.

I have created index.js file in nodejs to do so, which has the following code:

const neo4j = require('neo4j-driver').v1;
const driver = neo4j.driver("bolt://localhost", neo4j.auth.basic("neo4j", "testapp"));
const session = driver.session();
const async = require('async');
const appPathway = '/Users/reactor/Documents/testapp';
const country = require(appPathway+'/country');


async.eachSeries(country, (item, callback) => {
 
  const resPromise = session.run(
    `CREATE (c:country {label: "${item.label}", id: "${item.id}"}) RETURN c.id`
  );
  resPromise
  .then((data) => {
    return insertState(item.id);
              }
  )
  .then
   (
    (done) => {
    callback(null);
              }
    )
  .catch
  (
    (err) => {
    callback(err);
             }
  );
},

 (err) => {
  console.log(err);
  session.close();
  driver.close();
          }
  );


function insertState(countryID) {

  let state = require(appPathway+'/State/Country-'+countryID+'-statelist.js');


  return new Promise((resolve, reject) =>{
    async.eachSeries(state.items, (item1,item2, callback) => {
      
      const resPromise = session.run(
        `
        CREATE (s:state {label: "${item.label}", id: "${item.id}"})
        WITH s
        MATCH (c:Country)
        WHERE c.id = '${countryID}'
        CREATE (s)-[r:LOCATED_IN]->(c)
        RETURN c,s
        `
      );
      resPromise
      .then((state) => {
        console.log(state);
        callback(null);
      })
      resPromise
      .then((data) => {
        return insertCity(item1.id,item2.id);
      })
      .then((done) => {
        callback(null);
                  }
        )
    
      .catch((err) => {
        callback(err);
      });
    }, (err) => {
      if(err) {
        reject(err);
      }
      resolve(true);
    });
 }
);
}

// Problem rose when i inserted the following block of  code !!

function insertCity(countryID,stateID)  {
  let city = require(appPathway+'/city/Country-'+countryID+'-state-'+stateID+'-list.js');

  return new Promise((resolve, reject) =>
                  {
    async.eachSeries(city.items, () => {

      const resPromise = session.run(
        `
        CREATE (w:city {label: "${item.label}", id: "${item.id}"})
        WITH w
        MATCH (s:state)
        WHERE s.id = '${stateID}'

        /* How am I suppose to use the countryid parameter here in this cypher query ? As it doesn't have direct relation with label "country" in this query */
             
        CREATE (w)-[r:PRESENT_IN]->(s)
        RETURN w
        `
      );
      resPromise
      .then((city) => {
        console.log(city);
        callback(null);
      })
      .then((done) => {
        callback(null);
      })
      .catch((err) => {
        callback(err);
      });
      }, (err) => {
      if(err) {
        reject(err);
      }
      resolve(true);
      });
               }
      );
}

I am new to ES6,cypher and promise function which may have caused this problem. Although, I have looked into most of the posts, blogs and videos related to multiple promise chaining, but still I am unable to figure out how to do it when multiple parameters are present in a single js file and how to use these parameters to pull the data using cypher query.

Any help or suggestion would be really helpful for me now ! Thanks in Advance

cybersam cybersam · Accepted Answer · 2017-06-05T22:27:00

In insertState() and insertCity(), you are trying to dereference item.label and item.id, but there is no item in scope.

Getting "ReferenceError" error while performing multiple chaining of promise in nodejs application for neo4j import using cypher query

1 Answers