Trouble listing files with fs.readdir() in Node.js

Question

I'm working my way through the "Learn You The Node.js For Much Win!" workshop but I'm having trouble on exercise 5. It asks you to Create a program that prints a list of files in a given directory, filtered by the extension of the files.

I passed in the directory, files, that contains an assortment of JavaScript, Ruby, and plain text files. It is supposed to console.log() each file with the .js extension.

var fs = require('fs');

function indexDirectory(directory) {
  fs.readdir(directory, function(err, files) {
    for (var i in files) {
      if (i.indexOf('.js') != -1) {
        console.log(files[i]);
      }
    }
  });
}

indexDirectory('files');

My current code does not output anything when I run it with node program.js. Am I missing some asynchronous principle? Am I using callbacks incorrectly? Any help would be appreciated :)

A for in loop iterates over keys, not values; don’t use it on arrays. files.forEach(function (i) { … }). See also stackoverflow.com/questions/500504/…. — Ry-
– Ry- ♦, Commented Nov 30, 2014 at 19:37
for (var i = 0, file; i < files.length; i++) { file = files[i]} || files.forEach(function (file) {}); || files.filter(function(file){ return FILE_IS_JS; }); — generalhenry
– generalhenry, Commented Nov 30, 2014 at 19:39

Oleksandr T. · Accepted Answer · 2016-10-16 15:02:21Z

3

files are array, you should use forEach instead of for .. in

var fs = require('fs');

function indexDirectory(directory) {
  fs.readdir(directory, function(err, files) {
    files.forEach(function (file) {
      if (file.indexOf('.js') != -1) {
        console.log(file);
      }
    });  
  });
}

indexDirectory('files');

edited Oct 16, 2016 at 15:02

answered Nov 30, 2014 at 19:39

Oleksandr T.

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Comments

dmitreyg · Accepted Answer · 2014-11-30 19:48:27Z

0

One more problem with this code is that it will print also files with '.json' extension. So instead of indexOf you should use, for example, regular expressions. Something like this:

var matches = new RegExp(".js$").test(files[i]);
if (matches) {
   console.log(files[i]);
}

answered Nov 30, 2014 at 19:48

dmitreyg

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