writeFile - fs - Node

function writeFile

Usage in Deno

import { writeFile } from "node:fs";



writeFile(file: PathOrFileDescriptor,
data: string | ArrayBufferView,
options: WriteFileOptions,
callback: NoParamCallback,
): void

<div class="alert alert-warning"><div><svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"> <path stroke="none" d="M0 0h24v24H0z" fill="none" /> <path d="M12 9v4" /> <path d="M10.363 3.591l-8.106 13.534a1.914 1.914 0 0 0 1.636 2.871h16.214a1.914 1.914 0 0 0 1.636 -2.87l-8.106 -13.536a1.914 1.914 0 0 0 -3.274 0z" /> <path d="M12 16h.01" /> </svg> Deno compatibility</div><div><p> Missing <code>utf16le</code>, <code>latin1</code> and <code>ucs2</code> encoding.</p> </div></div>

When file is a filename, asynchronously writes data to the file, replacing the file if it already exists. data can be a string or a buffer.

When file is a file descriptor, the behavior is similar to calling fs.write() directly (which is recommended). See the notes below on using a file descriptor.

The encoding option is ignored if data is a buffer.

The mode option only affects the newly created file. See open for more details.

import { writeFile } from 'node:fs';
import { Buffer } from 'node:buffer';

const data = new Uint8Array(Buffer.from('Hello Node.js'));
writeFile('message.txt', data, (err) => {
  if (err) throw err;
  console.log('The file has been saved!');
});

If options is a string, then it specifies the encoding:

import { writeFile } from 'node:fs';

writeFile('message.txt', 'Hello Node.js', 'utf8', callback);

It is unsafe to use fs.writeFile() multiple times on the same file without waiting for the callback. For this scenario, createWriteStream is recommended.

Similarly to fs.readFile - fs.writeFile is a convenience method that performs multiple write calls internally to write the buffer passed to it. For performance sensitive code consider using createWriteStream.

It is possible to use an AbortSignal to cancel an fs.writeFile(). Cancelation is "best effort", and some amount of data is likely still to be written.

import { writeFile } from 'node:fs';
import { Buffer } from 'node:buffer';

const controller = new AbortController();
const { signal } = controller;
const data = new Uint8Array(Buffer.from('Hello Node.js'));
writeFile('message.txt', data, { signal }, (err) => {
  // When a request is aborted - the callback is called with an AbortError
});
// When the request should be aborted
controller.abort();

Aborting an ongoing request does not abort individual operating system requests but rather the internal buffering fs.writeFile performs.

Parameters



file: PathOrFileDescriptor

filename or file descriptor



data: string | ArrayBufferView



options: WriteFileOptions



callback: NoParamCallback

Return Type

void



writeFile(path: PathOrFileDescriptor,
data: string | ArrayBufferView,
callback: NoParamCallback,
): void

Asynchronously writes data to a file, replacing the file if it already exists.

Parameters



path: PathOrFileDescriptor

A path to a file. If a URL is provided, it must use the file: protocol. If a file descriptor is provided, the underlying file will not be closed automatically.



data: string | ArrayBufferView

The data to write. If something other than a Buffer or Uint8Array is provided, the value is coerced to a string.



callback: NoParamCallback

Return Type

void