Node.js recursively list full path of files

Question

Good night everyone. I'm having trouble with probably some simple recursive function. The problem is to recursively list all files in a given folder and its subfolders.

For the moment, I've managed to list files in a directory using a simple function:

fs.readdirSync(copyFrom).forEach((file) => {
  let fullPath = path.join(copyFrom, file);

  if (fs.lstatSync(fullPath).isDirectory()) {
    console.log(fullPath);
  } else {
    console.log(fullPath);
  }
});

I've tried various methods like do{} ... while() but I can't get it right. As I'm a beginner in javascript, I finally decided to ask for help from you guys.

You can use `recursive-readdir` package for this. https://www.npmjs.com/package/recursive-readdir — Kirill, May 01 '18 at 18:35
I would say Good day to you from another timezone and that you should maybe also read this: https://meta.stackexchange.com/questions/2950/should-hi-thanks-taglines-and-salutations-be-removed-from-posts — Endless, May 01 '18 at 18:36
Thanks @Kirill, I'll give it a try but as recursive functions seemed to be quite common I would have liked to understand how to do it :) — Puka, May 01 '18 at 18:40

score 20 · Accepted Answer · answered May 01 '18 at 18:39

20

Just add a recursive call and you are done:

 function traverseDir(dir) {
   fs.readdirSync(dir).forEach(file => {
     let fullPath = path.join(dir, file);
     if (fs.lstatSync(fullPath).isDirectory()) {
        console.log(fullPath);
        traverseDir(fullPath);
      } else {
        console.log(fullPath);
      }  
   });
 }

answered May 01 '18 at 18:39

Jonas Wilms

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Thanks, it seems to do the trick. However, I'm not having any console messages when executing the function... I must have missed something. – Puka May 01 '18 at 18:45
2

@YouDeserveThat, maybe a dumb question, but are you actually calling the function and not just defining it? – Fissure King May 01 '18 at 18:46
Hm. Dumb questions often help beginners :D. Thanks @FissureKing ! – Puka May 01 '18 at 18:47
2

@YouDeserveThat Just call the function like: `traverseDir(copyFrom);`. Also, accept the answer if it solves your problem :D – ibrahim mahrir May 01 '18 at 18:49
Thanks so much all of you, you saved my night ;) – Puka May 01 '18 at 18:56
@JonasW. a perfect use case for `unfold` <3 – Mulan May 01 '18 at 19:13
5

Don't forget to import path `var path = require('path');` – Julito Sanchis Sep 19 '18 at 09:28

Mulan · Answer 2 · 2018-05-01T20:01:16.120

Using console.log in this way displays the path and that's great, but what if you want to do something more meaningful with the paths? For example, maybe you want to collect all of them in an array and pass them off for processing elsewhere...

This process of beginning with a seed state and expanding a sequence of values while the state changes is called an unfold.

const { join } =
  require ('path')

const { readdirSync, statSync } =
  require ('fs')

const unfold = (f, initState) =>
  f ( (value, nextState) => [ value, ...unfold (f, nextState) ]
    , () => []
    , initState
    )

const None =
  Symbol ()

const relativePaths = (path = '.') =>
  readdirSync (path) .map (p => join (path, p))

const traverseDir = (dir) =>
  unfold
    ( (next, done, [ path = None, ...rest ]) =>
        path === None
          ? done ()
          : next ( path
                 , statSync (path) .isDirectory ()
                     ? relativePaths (path) .concat (rest)
                     : rest
                 )
    , relativePaths (dir)
    )

console.log (traverseDir ('.'))
// [ a, a/1, a/1/1, a/2, a/2/1, a/2/2, b, b/1, ... ]

If this is your first time seeing a program like this, unfold will feel very overwhelming. Below, is a simplified example of unfold used to generate an array of the lowercase alphabet

const unfold = (f, init) =>
  f ( (x, next) => [ x, ...unfold (f, next) ]
    , () => []
    , init
    )

const nextLetter = c =>
  String.fromCharCode (c.charCodeAt (0) + 1)

const alphabet =
  unfold
    ( (next, done, c) =>
        c > 'z'
          ? done ()
          : next ( c              // value to add to output
                 , nextLetter (c) // next state
                 )
    , 'a' // initial state
    )

console.log (alphabet)
// [ a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z ]

If you're still stuck, the techniques I've demonstrated here are explained in greater detail in answers to similar questions

Generally, it's preferred to use the asynchronous functions in the fs module as this prevents the program from hanging in the event of long disk read times or network delay. Unfolding plays nicely with asynchrony as demonstrated in these other Q&A's

Thanks for the really detailed anwser, I'll give it a try tomorrow :) — Puka, May 01 '18 at 19:57
@YouDeserveThat my pleasure. I've recently learned about [anamorphisms](https://en.wikipedia.org/wiki/Anamorphism) and I see use cases for them everywhere now! Let me know if you have any questions, I'm happy to help :D — Mulan, May 01 '18 at 19:58

Node.js recursively list full path of files

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