Store fs.stat while looping through files into an array, in Node JS

Question

I'm looping through files in a directory and storing the file details to an array data. The following code populates the array if I don't attempt to run fs.stat to get things like the file create/edit date:

fs.readdir('../src/templates', function (err, files) {
     if (err) {
        throw err;
      }
      var data = [];
      files
      .forEach(function (file) {
        try {
          fs.stat('../src/templates/'+file,(error,stats) => {
            data.push({ Name : file,Path : path.join(query, file)  });
          });
        } catch(e) {
          console.log(e);
        }

      });

      res.json(data);
  });
});

If I move the data.push(...) outside the fs.stat the array returns with the file data. Inside the fs.stat it returns empty. I assume this is an asynchronous issue in that the for loop is running and finishing before fs.stat runs.

I'm thinking I need to use a promise here but unsure.

Answer 1

If you want or need to be asynchronous:

const fs = require("fs");
const path = require("path");
const { promisify } = require("util");

const asyncStat = promisify(fs.stat);

fs.readdir('../src/templates', async function(err, files) {
  if (err) {
    throw err;
  }
  const data = await Promise.all(files.map(async function(file) {
    try {
      const stats = await asyncStat('../src/templates/' + file);
      return { Name: file, Path: path.join(query, file), stats };
    } catch (e) {
      console.log(e);
    }
  }));
  res.json(data);
});

Note that I used map instead of forEach and then awaited all Promises (async makes function return a promise). I also needed to change fs.stat to use promise with util.promisify.

Answer 2

You're right about the issue being in the asynchronous call. You could use a promise, or you could use fs.statSync(...), which returns a fs.Stats object and operates synchonously.

files.forEach(function (file) {
    try {
        var fileStats = fs.statSync('../src/templates/' + file);
        data.push({ 
            Name : file,
            Path : path.join(query, file)  
        });
    } catch(e) {
        console.log(e);
    }
});