nodejs: Not able to read response from callback function in the main function

Question

Noob in nodejs here and still trying to learn how nodejs works. Could you please let me know how can I pass the callback response from "getDatafromCosmosDB" function into a variable in the main function and print those values.

When I try to assign getDatafromCosmosDB to a variable "respdata" and try to print it, it is not working.

async function main(params, callback) {
    const logger = Core.Logger('main2', { level: params.LOG_LEVEL || 'info' })
    try {
        logger.info('main action')
        const respdata = getDatafromCosmosDB(function(response){
            console.debug(response)
            return response
        });
         console.debug(respdata)
    } catch (e) {
        console.debug(e)
    }
}

exports.main = main
async function getDatafromCosmosDB(callback){
    var query = new azure.TableQuery()
    .top(5)
    tableService.queryEntities('myCosmosTable', query, null, function (error, result, response) {
        if (!error) {
            console.log('success')
            return callback(result.entries)
        }
    });
}

Does this answer your question? [nodeJs callbacks simple example](https://stackoverflow.com/questions/19739755/nodejs-callbacks-simple-example) — yeya, May 10 '21 at 14:28
That helps quite a bit, thank you. I was also looking for some examples as well and below answer helps as well! — Scorpyon, May 26 '21 at 05:29

score 1 · Accepted Answer · answered May 10 '21 at 16:31

Try something like this,

import {
  createTableService,
  services,
  ServiceResponse,
  TableQuery
} from 'azure-storage';

getDatafromCosmosDB(): Promise<ServiceResponse> {
 return new Promise(async (resolve, reject) => {
       this.tableService.queryEntities(
        this.tableName,
        query,
        null,
        (error, _, response) => {
          if (!error) {
            resolve(response);
          } else {
            reject(error);
          }
        }
      );
    });
}

and invoke like,

this.getDatafromCosmosDB().then(data => {
  console.log(data);
}

nodejs: Not able to read response from callback function in the main function

1 Answers1