How to read a file line by line into an array in node.js

Question

I need to be able to read a simple text file that contains a series of numbers for each line.

These numbers need to be read and stored somewhere in my code so I figure an array is the best way to go. Once the array has the values stored I can use it for further manipulation but I can't seem to actually read and push values into my array from each line in a text file.

What's the best way to do this? All help is appreciated! Thanks!

Cheers https://stackoverflow.com/questions/6831918/node-js-read-a-text-file-into-an-array-each-line-an-item-in-the-array — Hasan Huseyin Ozkaya, Jul 20 '17 at 08:15

score 13 · Answer 1 · answered Jul 20 '17 at 08:24

var fs = require('fs');
var readline = require('readline');
var stream = require('stream');

var instream = fs.createReadStream('./test.txt');
var outstream = new stream;
var rl = readline.createInterface(instream, outstream);

var arr = [];

rl.on('line', function(line) {
  // process line here
  arr.push(line);
});

rl.on('close', function() {
  // do something on finish here
  console.log('arr', arr);
});

This approach also handles large text file. https://coderwall.com/p/ohjerg/read-large-text-files-in-nodejs

Is there anyway to return the array instead of logging it ot the console (in the case where the above code was inside of a function)? — Dianne, Mar 08 '22 at 21:22

score 2 · Answer 2 · answered Jul 20 '17 at 08:14

Check out this answer.

This is the solution proposed there:

var lineReader = require('readline').createInterface({
  input: require('fs').createReadStream('file.in')
});

lineReader.on('line', function (line) {
  console.log('Line from file:', line);
});

Has also been added to the Node docs.

How to read a file line by line into an array in node.js

2 Answers2