javascript - Should I use promise for mkdir - Stack Overflow

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I use the bluebird magic

var fs = Promise.promisifyAll(require('fs'));

and use

fs.readdirAsync(dest).then(function (val) {
        return val;
}).then(function (file) {

...

My question is for the following code (which is working) should I use the same and how I am talking about the mkdir function.

function createDir(folder) {
    return function (req, res, next) {
        if (typeof require.cache.per === 'undefined') {
            require.cache.per = {};
            require.cache.per.mk = false;
        }
        if (!require.cache.per.mk) {
            fs.mkdir(folder, function (e) {
                if (!!e && e.code !== 'EEXIST') {
                    console.log('Error to create  folder: ' + err);
                }
                require.cache.per.mk = true;
                next();
            });
        } else {
            next();
        }
    };
}

My Question is should I use promise here or not, what is remended ? The code is working as expected...

I use the bluebird magic

var fs = Promise.promisifyAll(require('fs'));

and use

fs.readdirAsync(dest).then(function (val) {
        return val;
}).then(function (file) {

...

My question is for the following code (which is working) should I use the same and how I am talking about the mkdir function.

function createDir(folder) {
    return function (req, res, next) {
        if (typeof require.cache.per === 'undefined') {
            require.cache.per = {};
            require.cache.per.mk = false;
        }
        if (!require.cache.per.mk) {
            fs.mkdir(folder, function (e) {
                if (!!e && e.code !== 'EEXIST') {
                    console.log('Error to create  folder: ' + err);
                }
                require.cache.per.mk = true;
                next();
            });
        } else {
            next();
        }
    };
}

My Question is should I use promise here or not, what is remended ? The code is working as expected...

• javascript
• promise
• bluebird

Share Improve this question Follow edited Feb 25, 2016 at 13:08 asked Feb 25, 2016 at 10:51 user4445419user4445419 8

• 1 You can just use mkdirAsync, promisifyAll creates it for you. – Benjamin Gruenbaum Commented Feb 25, 2016 at 14:22
• @BenjaminGruenbaum -Thanks but how should I call it with the catch and the next inside promise ,can you please provide example? – user4445419 Commented Feb 25, 2016 at 14:27
• Exactly the same way you did for readdir – Benjamin Gruenbaum Commented Feb 25, 2016 at 14:43
• it is remended to use promise for an async call. so use the same way that used for readdir – Raja Sekar Commented Mar 1, 2016 at 12:16
• That must be your choice. If u want use it - go ahead, if u OK with callbacks - ok :). Btw what the reason using !!e :) ? – loadaverage Commented Mar 8, 2016 at 0:53

 |  Show 3 more ments

3 Answers 3

Sorted by: Reset to default 6 +25

A Promise simplifies, and unifies the interface. Either .promisify() or .promisifyAll() will do the trick.

Then you can chain everything like this:

fs.mkdir(dir)
    .then(function success(dir) {
        ...
    })
    .catch(function failure(err) {
        ...
    })
    .finally(function () {
    });

However in node.js, the most important thing is to NOT block the I/O. It doesn't matter whether you use a Promise or a regular async/callback, as long as it's not blocking the main thread.

It's ok to have synchronous code in script that you want to run in shell, but for regular applications you should never use blocking I/O operations on purpose.

I would definitely update your code to be consistent. If possible, call mkdirAsync instead of mkdir

Example (from OP's code):

var fs = Promise.promisifyAll(require('fs'));

// ...

fs.mkdirAsync(folder)
   .catch({ code: 'EEXIST' }, function(e){
       // don't care about this error code  
   })
   .catch(function(e) {
       console.log('Error to create  folder: ' + e);
   })
   .then(function(){
       require.cache.per.mk = true;
       next();
   });

Promise.promisifyAll(fs);

return fs.mkdirAsync(dir1)
  .then(function() {
    return fs.mkdirAsync(dir2);
  })
  .then(function() {
    return fs.mkdirAsync(dir3);
  })

Hope this helps.

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