How do you get a folder map as a JSON in Node.js asynchronously?

Question

I've tried implementing the code from here, but I have problem with asynchronous function.

I wanted to get a folder map through a function like this:

getFolderMap("./public", function(folderMap){
    /* Call back */
});

And the function would return sth. like this:

{
    "index":{"fileType":"html", blah blah blah...}
    "assets":{
        "plants":{
            "plant1":{"fileType":"png", blah blah blah...}
        }
    }
    "css":{
        "style":{"fileType":"css", blah blah blah...}
        "flickity":{"fileType":"css", blah blah blah...}
    },
    "js":{
        "main":{"fileType":"js", blah blah blah...}
    }
}

The code was:

var getFolderMap = function(rootDir, cb) { 
    fs.readdir(rootDir, function(err, files) { 
        var dirs = {};
        for (var index = 0; index < files.length; index++) { 
            var file = files[index]; 
            if (file[0] !== '.') { 
                var filePath = rootDir + '/' + file; 
                fs.stat(filePath, function(err, stat) {
                    if (stat.isDirectory()) {
                        var file = this.file;
                        //Recursion...
                        getFolderMap(this.filePath,function(d){
                            dirs[file]=d;
                        });
                    }else{
                        dirs[this.file] = {
                            fileType: ""
                        };
                    }
                    if (files.length === (this.index + 1)) { 
                        return cb(dirs); 
                    } 
                }.bind({index: index, file: file, filePath:filePath})); 
            }
        }
    });
};

Can you share your code? And what error are you running into? — Arun Kumar Mohan, Feb 14 '21 at 05:52
There's no error, but the result is returned before the handeler is called. — 猫ハッカー, Feb 14 '21 at 06:15
can you use `for of` with async/await instead of for with callback? @猫ハッカー — Mohammad Yaser Ahmadi, Feb 14 '21 at 06:32
Never herd of `for ... of` loop before... let me check it. I'm self-taught, so I don't know much about these rare keywords. — 猫ハッカー, Feb 14 '21 at 06:37

Arun Kumar Mohan · Answer 1 · 2021-02-14T09:27:44.383

1

You can use async/await and Promise.all to simplify the orchestration of the async operations.

const { readdir, stat } = require('fs').promises
const { extname } = require('path')

const generateFolderMap = async (rootDir) => {
  const files = await readdir(rootDir)

  const map = {}
  await Promise.all(
    files.map(async (file) => {
      if (file[0] === '.') {
        return null
      }

      const filePath = rootDir + '/' + file
      const stats = await stat(filePath)

      if (stats.isDirectory()) {
        map[file] = await generateFolderMap(filePath)
      } else {
        map[file] = { fileType: extname(file).slice(1) }
      }
    })
  )

  return map
}

edited Feb 14 '21 at 09:27

answered Feb 14 '21 at 07:11

Arun Kumar Mohan

11,517
3
23
44

I got an error `UnhandledPromiseRejectionWarning: ReferenceError: Cannot access 'readdir' before initialization` – 猫ハッカー Feb 14 '21 at 15:12
@猫ハッカー Can you share your code in a [gist](http://gist.github.com/) or something? – Arun Kumar Mohan Feb 14 '21 at 19:56

score 0 · Answer 2 · answered Feb 15 '21 at 16:30

0

I've decided that I'd be using the synchronous version, and it works perfectly. Though it made the server starting up pretty slowly. It's not a big problem though, I just wanted to find the best solution to my problem to speed up my server.

answered Feb 15 '21 at 16:30

猫ハッカー

52
5

How do you get a folder map as a JSON in Node.js asynchronously?

2 Answers2