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I have a sample array as follows

var arr = [ [ 1373628934214, 3 ],
  [ 1373628934218, 3 ],
  [ 1373628934220, 1 ],
  [ 1373628934230, 1 ],
  [ 1373628934234, 0 ],
  [ 1373628934237, -1 ],
  [ 1373628934242, 0 ],
  [ 1373628934246, -1 ],
  [ 1373628934251, 0 ],
  [ 1373628934266, 11 ] ]

I would like to write this array to a file such as I get a file as follows

1373628934214, 3 
1373628934218, 3
1373628934220, 1
......
......

I have a sample array as follows

var arr = [ [ 1373628934214, 3 ],
  [ 1373628934218, 3 ],
  [ 1373628934220, 1 ],
  [ 1373628934230, 1 ],
  [ 1373628934234, 0 ],
  [ 1373628934237, -1 ],
  [ 1373628934242, 0 ],
  [ 1373628934246, -1 ],
  [ 1373628934251, 0 ],
  [ 1373628934266, 11 ] ]

I would like to write this array to a file such as I get a file as follows

1373628934214, 3 
1373628934218, 3
1373628934220, 1
......
......

• javascript
• node.js

Share Improve this question Follow edited Jul 12, 2013 at 14:24 dopplesoldner asked Jul 12, 2013 at 11:39 dopplesoldnerdopplesoldner 9,4391212 gold badges4646 silver badges5656 bronze badges 0

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8 Answers 8

Sorted by: Reset to default 140

If it's a huuge array and it would take too much memory to serialize it to a string before writing, you can use streams:

var fs = require('fs');

var file = fs.createWriteStream('array.txt');
file.on('error', function(err) { /* error handling */ });
arr.forEach(function(v) { file.write(v.join(', ') + '\n'); });
file.end();

Remember you can access good old ECMAScript APIs, in this case, JSON.stringify().

For simple arrays like the one in your example:

require('fs').writeFile(

    './my.json',

    JSON.stringify(myArray),

    function (err) {
        if (err) {
            console.error('Crap happens');
        }
    }
);

To do what you want, using the fs.createWriteStream(path[, options]) function in an ES6 way:

const fs = require('fs');
const writeStream = fs.createWriteStream('file.txt');
const pathName = writeStream.path;
 
let array = ['1', '2', '3', '4', '5', '6', '7'];
  
// write each value of the array on the file breaking line
array.forEach(value => writeStream.write(`${value}
`));

// the finish event is emitted when all data has been flushed from the stream
writeStream.on('finish', () => {
   console.log(`wrote all the array data to file ${pathName}`);
});

// handle the errors on the write process
writeStream.on('error', (err) => {
    console.error(`There is an error writing the file ${pathName} => ${err}`)
});

// close the stream
writeStream.end();

A simple solution is to use writeFile :

require("fs").writeFile(
     somepath,
     arr.map(function(v){ return v.join(', ') }).join('\n'),
     function (err) { console.log(err ? 'Error :'+err : 'ok') }
);

async function x(){
var arr = [ [ 1373628934214, 3 ],
[ 1373628934218, 3 ],
[ 1373628934220, 1 ],
[ 1373628934230, 1 ],
[ 1373628934234, 0 ],
[ 1373628934237, -1 ],
[ 1373628934242, 0 ],
[ 1373628934246, -1 ],
[ 1373628934251, 0 ],
[ 1373628934266, 11 ] ];
await fs.writeFileSync('./PATH/TO/FILE.txt', arr.join('\n'));
}

We can simply write the array data to the filesystem but this will raise one error in which ',' will be appended to the end of the file. To handle this below code can be used:

var fs = require('fs');

var file = fs.createWriteStream('hello.txt');
file.on('error', function(err) { Console.log(err) });
data.forEach(value => file.write(`${value}\r\n`));
file.end();

\r\n

is used for the new Line.

\n

won't help. Please refer this

Try with this

await fs.writeFileSync('arreglo.txt', arreglo.join('\n '));

This code works for me

don't forget to import fs

import fs from 'fs';

const fs = require('fs');

var arr = [
  [1373628934214, 3],
  [1373628934218, 3],
  [1373628934220, 1],
  [1373628934230, 1],
  [1373628934234, 0],
  [1373628934237, -1],
  [1373628934242, 0],
  [1373628934246, -1],
  [1373628934251, 0],
  [1373628934266, 11]
];

const content = arr.map(item => item.join(', ')).join('\n');

const fp = 'output.txt';

fs.writeFileSync(fp, content, 'utf-8');

console.log('Array has been written to', fp);

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