Node.js - fs.writeFile() example

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:

Copy

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1

node file_name.js

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:

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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:

After:

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:

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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:

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:

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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: