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.