Zip file using yauzal lib

I’m using the following code to unzip file which is working OK.
I’m getting file with the request (express) and unzip it in specified folder

_unzip: function (req) {
        return new Promise((resolve, reject) =>{
            var noOfFiles = 0;
            let filePath = path.join(req.file.destination, req.file.filename);
            logger.info("Unzip filePath: " + filePath);
            if (req.file) {
                yauzl.open(filePath, function (err, zipFile) {
                    if (err) throw err;
                    zipFile.on('entry', (entry) =>{
                        //console.log(entry.fileName);
                        if (//$/.test(entry.fileName)) {
                            return;
                        }
                        zipFile.openReadStream(entry, (err, readStream) => {
                            if (err) {
                                logger.info(err);
                                reject(err);
                            } else {
                                // ensure parent directory exists, and then:
                                let destinationFileName = "./" + entry.fileName;

                                let directoryName = path.dirname(destinationFileName);
                                if (!fs.existsSync(directoryName)) {
                                    mkdirp(directoryName, (err) =>{
                                        if (err) {
                                            logger.info(err);
                                            reject(err);
                                        } else {
                                            writeIntoFile(readStream, destinationFileName, reject);
                                            noOfFiles++;
                                        }
                                    });
                                } else {
                                    writeIntoFile(readStream, destinationFileName, reject);
                                    noOfFiles++;
                                }
                            }
                        });
                    }).once('error', (err) =>{
                        logger.info(err);
                        reject(err);
                    }).once('close', () =>{
                        logger.info("Unpacked " + noOfFiles + " files");
                        resolve();
                    });
                });
            }
    });
}

https://github.com/thejoshwolfe/yauzl

• Check for req.file before using its properties
• Return/reject early instead of nesting a big else clause
• Since you’re using ES2015 syntax do it consistently:
  • template strings via backticks
  • arrow functions in callbacks that don’t utilize this of the callee
  • string methods with self-explanatory names like endsWith instead of regexps
  • let instead of var (there was one in your code)
• Deduplicate reject+logger combo and writeIntoFile
• Use single or double quotes consistently

return new Promise((resolve, reject) => {
    if (!req || !req.file) {
        __rejectAndLog('No file provided');
        return;
    }
    let numberOfFiles = 0;
    let filePath = path.join(req.file.destination, req.file.filename);
    logger.info(`Unzip filePath: ${filePath}`);

    yauzl.open(filePath, (err, zipFile) => {
        if (err) {
            __rejectAndLog(err);
            return;
        }
        zipFile.on('entry', entry => __processEntry(zipFile, entry))
            .once('error', __rejectAndLog)
            .once('close', () => {
                logger.info(`Unpacked ${numberOfFiles} files`);
                resolve();
            });
    });

    function __processEntry(zipFile, entry) {
        if (entry.fileName.endsWith('/')) {
            return;
        }

        zipFile.openReadStream(entry, (err, readStream) => {
            if (err) {
                __rejectAndLog(err);
                return;
            }

            let destinationFileName = './' + entry.fileName;
            let directoryName = path.dirname(destinationFileName);
            if (fs.existsSync(directoryName)) {
                __writeFile();
                return;
            }

            mkdirp(directoryName, (err) => {
                if (err) {
                    __rejectAndLog(err);
                } else {
                    __writeFile();
                }
            });

            function __writeFile() {
                writeIntoFile(readStream, destinationFileName, reject);
                numberOfFiles++;
            }
        });
    }

    function __rejectAndLog(err) {
        logger.info(err);
        reject(err);
    }
});

• entry-processing function is extracted to make the zipFile flow more obvious
• __ prefix is used for subfunctions following your naming of _unzip