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Node.js - fs.writeFile() example

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In this article, we would like to show you how to use fs.writeFile() in Node.js.

The fs.writeFile() method can be used to:

  • create new file (if file with the specified name doesn't exist),
  • update existing file.

Note:

You can copy each of the examples below and run the script with the following command in the terminal / cmd opened in your project's directory:

node file_name.js

1. Creating new txt file with fs.writeFile()

Below we create file.js file which creates new txt file in the same directory with some text inside.

Note:

If you want to create file in a different directory just specify relative path to the file as a fs.writeFile() first argument instead of just file name.

Practical example:

var fs = require('fs');  // imports File System Module

fs.writeFile('newFile.txt', 'file body here...', (error) => {
  if (error) throw error;
  console.log('Creating new .txt file');
});

Before:

Node.js - creating new file with fs.writeFile
Node.js - creating new file with fs.writeFile

After:

Node.js - creating new file with fs.writeFile
Node.js - creating new file with fs.writeFile

2. Updating txt file with fs.writeFile()

Below we create file.js file which updates existing txt file in the same directory with some text inside.

Note:

If you want to update file in a different directory just specify relative path to the file as a fs.writeFile() first argument instead of just file name.

Practical example:

var fs = require('fs');

var newFileBody = 'new txt file body';

fs.writeFile('newFile.txt', newFileBody, (error) {
  if (error) throw error;
  console.log('Updating .txt file');
});

Result:

Node.js - updating txt file with fs.writeFile
Node.js - updating txt file with fs.writeFile

3. fs.write() example

The fs.write() method creates a new file with given string or inserts the string at the end of the file if the file exists.

Practical example:

const fs = require('fs');

const str = 'dirask is awesome! \n';
const filename = 'input.txt';

fs.open(filename, 'a', (err, fd) => {
  if (err) {
    console.log(err.message);
  } else {
    fs.write(fd, str, (err, bytes) => {
      if (err) {
        console.log(err.message);
      } else {
        console.log(bytes + ' bytes written');
      }
    });
  }
  fs.close(fd, (err) => {
    if (err) console.error('failed to close file', err);
    else {
      console.log('\n> file closed');
    }
  });
});

Example result after running script two times:

Node.js - creating & updating txt file with fs.write()
Node.js - creating & updating txt file with fs.write()

Node.js - file system module

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