Looping through files in a folder Node.JS

Question

I am trying to loop through and pick up files in a directory, but I have some trouble implementing it. How to pull in multiple files and then move them to another folder?

Answer 1

The answers provided are for a single folder. Here is an asynchronous implementation for multiple folders where all the folders are processed simultaneously but the smaller folders or files gets completed first.

Please comment if you have any feedback

Asynchronously Multiple Folders

const fs = require('fs')
const util = require('util')
const path = require('path')

// Multiple folders list
const in_dir_list = [
  'Folder 1 Large',
  'Folder 2 Small', // small folder and files will complete first
  'Folder 3 Extra Large'
]

// BEST PRACTICES: (1) Faster folder list For loop has to be outside async_capture_callback functions for async to make sense
//                 (2) Slower Read Write or I/O processes best be contained in an async_capture_callback functions because these processes are slower than for loop events and faster completed items get callback-ed out first 

for (i = 0; i < in_dir_list.length; i++) {
  var in_dir = in_dir_list[i]

  // function is created (see below) so each folder is processed asynchronously for readFile_async that follows
  readdir_async_capture(in_dir, function(files_path) {
    console.log("Processing folders asynchronously ...")

    for (j = 0; j < files_path.length; j++) {
      file_path = files_path[j]
      file = file_path.substr(file_path.lastIndexOf("/") + 1, file_path.length)

      // function is created (see below) so all files are read simultaneously but the smallest file will be completed first and get callback-ed first 
      readFile_async_capture(file_path, file, function(file_string) {
        try {
          console.log(file_path)
          console.log(file_string)
        } catch (error) {
          console.log(error)
          console.log("System exiting first to catch error if not async will continue...")
          process.exit()
        }
      })
    }
  })
}

// fs.readdir async_capture function to deal with asynchronous code above
function readdir_async_capture(in_dir, callback) {
  fs.readdir(in_dir, function(error, files) {
    if (error) { return console.log(error) }
    files_path = files.map(function(x) { return path.join(in_dir, x) })
    callback(files_path)
  })
}

// fs.readFile async_capture function to deal with asynchronous code above
function readFile_async_capture(file_path, file, callback) {
  fs.readFile(file_path, function(error, data) {
    if (error) { return console.log(error) }
    file_string = data.toString()
    callback(file_string)
  })
}