Creating a temporary directory in node

Somehow this set of APIs slipped under the radar in my 10+ years of writing Node.js code.

I've been building a service that writes geospatial files to disk as it transforms them and discovered a set of native node APIs (that also exist in Deno) that allow you to create a temporary directory in the operating system's temporary directory folder.

Here's the code snippet that creates a temporary directory with a prefix:

import fs from "node:fs";
import os from "node:os";
import path from "node:path";

const createTempDirectory = (prefix = ""): string => {
  return fs.mkdtempSync(path.join(os.tmpdir(), prefix));
};

Lets break it down.

1. os.tmpdir() returns the operating system's default directory for temporary files.
2. path.join() joins the operating system's temporary directory with the prefix you provide.
3. fs.mkdtempSync() creates a temporary directory with the prefix you provided and returns the path to the directory.

Asynchronous approaches

There is also a couple of async options available in the fs module to create temporary directories.

Callback Version

import fs from "node:fs";
import os from "node:os";
import path from "node:path";

const createTempDirectory = (prefix = "", callback: (err: NodeJS.ErrnoException | null, folder: string) => void) => {
  fs.mkdtemp(path.join(os.tmpdir(), prefix), callback);
};

Promise Version

import fs from "node:fs/promises";
import os from "node:os";
import path from "node:path";

const createTempDirectory = (prefix = ""): Promise<string> => {
  return fs.mkdtemp(path.join(os.tmpdir(), prefix));
};

Automatic Cleanup

There is now an pathway in Javascript to automatically cleanup the temporary directory when you're done with it the handle using the Explicit Resource Management functionality landing in JS environments near you. When its settled and better documentation is available, I'll likely write a follow up post on how to use it.

Non-Automatic Cleanup

For now, the cleanup of the temporary directory is left to the developer. You can use the fs.rmdirSync function to remove the directory when you're done with it.

const tempDir = createTempDirectory("my-prefix");
// Do something with the directory
fs.rmdirSync(tempDir, { recursive: true });
// or to get something similar to the `rm -rf` command
fs.rmSync(tempDir, { recursive: true, force: true });