test.js

var fs = require('fs');

function existTest() {
    fs.exists("./test/", function (exists) {
        setTimeout(function () {
            if (exists) {
                fs.writeFile("./test/test.txt", "aaljdks", function (err) {
                    if (err) {
                        //Maybe permissions or disk full
                        throw err;
                    }
                });
            } else {
                //Try to create the Dir
                fs.mkdir("./test/", function (err) {
                    if (err) {
                        //Maybe permissions ot the dir exists now
                        if (err.code !== 'EEXIST') {
                            throw err;
                        }
                    }

                    fs.writeFile("./test/test.txt", "aaljdks", function (err) {
                        if (err) {
                            //Maybe permissions or disk full
                            throw err;
                        }
                    });
                });
            }
        }, 50);
    });
}

function writeFailureTest() {
    //Try to write data
    fs.writeFile("./test/test.txt", "aaljdks", function (err) {
        if (err) {
            //Maybe permissions or disk full or the dir does not exist
            console.log(err); //<= Gives ENOENT Error
        }

        fs.mkdir("./test/", function (err) {
            if (err) {
                //Maybe permissions ot the dir exists now
            }

            fs.writeFile("./test/test.txt", "aaljdks", function (err) {
                if (err) {
                    //Maybe permissions or disk full
                }
            });
        });
    });
}

existTest();
writeFailureTest();
existTest();
writeFailureTest();
existTest();
writeFailureTest();