how to access a local variable value outside the scope of its function in nodejs

Question

I want to compare the data of two files and for that, I'm reading that file using the fs module but since I want to compare the values so I thought to store the value in an external variable but when I do console.log(budget_details) I get nothing in console. Please someone help. Please point me out if my approach is wrong and if we don't need to do that in nodejs. I'm new to nodejs.

import csv from 'csv-parser'
import fs from 'fs';

let budget_details
const budgetProcessing = (budget_file_path) => {
    try{
        fs.createReadStream(budget_file_path)
            .pipe(csv())
            .on('data', (row) => {
                budget_details = row
            })
            .on('end', () => {
                console.log('CSV file successfully processed');
            });
    }
    catch(error){
        console.log(error)
    }
}

budgetProcessing('budget.csv')

console.log(budget_details)

Answer 1

your code is not asynchronous. Anything with 'on', which takes a function, would indicate that it is event driven. You need something like:

import csv from 'csv-parser'
import fs from 'fs';

let budget_details
const budgetProcessing = (budget_file_path) => new Promise((resolve, reject) => {
  try {
    fs.createReadStream(budget_file_path)
      .pipe(csv())
      .on('data', (row) => {
        budget_details = row
      })
      .on('end', () => {
        console.log('CSV file successfully processed');
        resolve()
      });
  } catch (error) {
    console.log(error)
    reject(error)
  }
})

budgetProcessing('budget.csv')
  .then(() => console.log(budget_details))