How to write file if parent folder doesn't exist?

As of Node v10, this is built into the fs.mkdir function, which we can use in combination with path.dirname:

var fs = require('fs');var getDirName = require('path').dirname;function writeFile(path, contents, cb) {  fs.mkdir(getDirName(path), { recursive: true}, function (err) {    if (err) return cb(err);    fs.writeFile(path, contents, cb);  });}

For older versions, you can use mkdirp:

var mkdirp = require('mkdirp');var fs = require('fs');var getDirName = require('path').dirname;function writeFile(path, contents, cb) {  mkdirp(getDirName(path), function (err) {    if (err) return cb(err);        fs.writeFile(path, contents, cb);  });}

If the whole path already exists, mkdirp is a noop. Otherwise it creates all missing directories for you.

This module does what you want: https://npmjs.org/package/writefile . Got it when googling for "writefile mkdirp". This module returns a promise instead of taking a callback, so be sure to read some introduction to promises first. It might actually complicate things for you.

The function I gave works in any case.

I find that the easiest way to do this is to use the outputFile() method from the fs-extra module.

Almost the same as writeFile (i.e. it overwrites), except that if the parent directory does not exist, it's created. options are what you'd pass to fs.writeFile().

Example:

var fs = require('fs-extra');var file = '/tmp/this/path/does/not/exist/file.txt'fs.outputFile(file, 'hello!', function (err) {    console.log(err); // => null    fs.readFile(file, 'utf8', function (err, data) {        console.log(data); // => hello!    });});

It also has promise support out of the box these days!.

Edit

NodeJS version 10.12.0 has added a native support for both mkdir and mkdirSync to create the parent director recursively with recursive: true option as the following:

fs.mkdirSync(targetDir, { recursive: true });

And if you prefer fs Promises API, you can write

fs.promises.mkdir(targetDir, { recursive: true });

Original Answer

Create the parent directories recursively if they do not exist! (Zero dependencies)

const fs = require('fs');const path = require('path');function mkDirByPathSync(targetDir, { isRelativeToScript = false } = {}) {  const sep = path.sep;  const initDir = path.isAbsolute(targetDir) ? sep : '';  const baseDir = isRelativeToScript ? __dirname : '.';  return targetDir.split(sep).reduce((parentDir, childDir) => {    const curDir = path.resolve(baseDir, parentDir, childDir);    try {      fs.mkdirSync(curDir);    } catch (err) {      if (err.code === 'EEXIST') { // curDir already exists!        return curDir;      }      // To avoid `EISDIR` error on Mac and `EACCES`-->`ENOENT` and `EPERM` on Windows.      if (err.code === 'ENOENT') { // Throw the original parentDir error on curDir `ENOENT` failure.        throw new Error(`EACCES: permission denied, mkdir '${parentDir}'`);      }      const caughtErr = ['EACCES', 'EPERM', 'EISDIR'].indexOf(err.code) > -1;      if (!caughtErr || caughtErr && curDir === path.resolve(targetDir)) {        throw err; // Throw if it's just the last created dir.      }    }    return curDir;  }, initDir);}

Usage

// Default, make directories relative to current working directory.mkDirByPathSync('path/to/dir');// Make directories relative to the current script.mkDirByPathSync('path/to/dir', {isRelativeToScript: true});// Make directories with an absolute path.mkDirByPathSync('/path/to/dir');

Demo

Try It!

Explanations

• [UPDATE] This solution handles platform-specific errors like EISDIR for Mac and EPERM and EACCES for Windows.
• This solution handles both relative and absolute paths.
• In the case of relative paths, target directories will be created (resolved) in the current working directory. To Resolve them relative to the current script dir, pass {isRelativeToScript: true}.
• Using path.sep and path.resolve(), not just / concatenation, to avoid cross-platform issues.
• Using fs.mkdirSync and handling the error with try/catch if thrown to handle race conditions: another process may add the file between the calls to fs.existsSync() and fs.mkdirSync() and causes an exception.
  • The other way to achieve that could be checking if a file exists then creating it, I.e, if (!fs.existsSync(curDir) fs.mkdirSync(curDir);. But this is an anti-pattern that leaves the code vulnerable to race conditions.
• Requires Node v6 and newer to support destructuring. (If you have problems implementing this solution with old Node versions, just leave me a comment)