How to read a CSV file in JavaScript

Short answer

For simple files, split the text into lines and each line by commas. The first line holds the column names:

const csv = 'name,city,age\nAnna,Rome,30\nOleg,Paris,25';
 
const [header, ...rows] = csv.split('\n').map((line) => line.split(','));
const people = rows.map((row) => Object.fromEntries(header.map((key, i) => [key, row[i]])));
 
console.log(people[1].city);
console.log(JSON.stringify(people[0]));

Output:

Paris
{"name":"Anna","city":"Rome","age":"30"}

From a file in Node.js

Read the file and apply the same parsing:

import { readFile, writeFile } from 'node:fs/promises';
 
await writeFile('prices.csv', 'item,price\ntea,3.5\ncake,4\n');
 
const lines = (await readFile('prices.csv', 'utf8')).trim().split(/\r?\n/);
const total = lines.slice(1).reduce((sum, line) => sum + Number(line.split(',')[1]), 0);
 
console.log(total);

Output:

7.5

Values in quotes

Values with commas are wrapped in quotes. A regular expression can take a quoted value as a whole:

const parseLine = (line) =>
  [...line.matchAll(/"((?:[^"]|"")*)"|([^,]+)|(?<=,|^)(?=,|$)/g)].map((m) =>
    m[1] !== undefined ? m[1].replaceAll('""', '"') : m[2] ?? '',
  );
 
console.log(parseLine('Anna,"Rome, Italy",30'));

Output:

[
  "Anna",
  "Rome, Italy",
  "30"
]

Common mistake

A plain split(',') breaks values that contain commas. For real files with quotes and line breaks inside values, use a ready CSV library.

console.log('Anna,"Rome, Italy",30'.split(',').length);

Output:

Thanks for reading!

Short answer

From a file in Node.js

Values in quotes

Common mistake

Functions used in this recipe

Thanks for reading!