Parse csv using "csv-parser" node JS-CodePudding

I am using the 'csv-parser' library. Using the method below I am able to get the data stored in the birthdays array shown in the console:

    const birthdays = [];  
fs.createReadStream('./data/groupes.csv')
        .pipe(csv({}))
        .on('data', (data) => birthdays.push(data))
        .on('end', () => {
          console.log(birthdays)
      });

but when I log outside the .on('end') like below, the console shows the birthdays array as empty:

    const birthdays = [];  
fs.createReadStream('./data/groupes.csv')
        .pipe(csv({}))
        .on('data', (data) => birthdays.push(data))
        .on('end', () => {
      });
      console.log(birthdays)

Why is that? and how can I solve it? Thanks in advance.

CodePudding user response：

Could you do something like this?

const csv = require("csv-parser");
const fs = require("fs");
const path = require("path");
const { promisify } = require("util");
const readFile = promisify(fs.readFile);

const birthdays = [];

const filePath = path.join(__dirname, "data", "groupes.csv");

readFile(filePath, "utf8").then((data) => {
  csv(data, {
    separator: ",",
  })
    .on("data", (row) => {
      birthdays.push(row);
    })
    .on("end", () => {
      console.log(birthdays);
    });
});

CodePudding user response：

Why is that?

It's because createReadStream is working asynchronously and when you console.log(birthdays); outside, the code execution reads the log before createReadStream has finished processing

how can I solve it?

You were correct to put it inside the .on("end")

const birthdays = [];  
fs.createReadStream('./data/groupes.csv')
    .pipe(csv({}))
    .on('data', (data) => birthdays.push(data))
    .on('end', () => {
      console.log(birthdays);
      // further processing with birthdays
  });