I am trying to write a function that will read a file and depending upon success or failure in reading it will call the resolve or reject function. Below is the code that I have written.
let fs = require('fs');
const FILE_NAME = './assets/pies.json';
let pieRepo = {
get: function(resolve, reject) {
fs.readFile(FILE_NAME, function(err, data) {
if(err) {
reject(err);
}
else {
resolve(JSON.parse(data));
}
});
}
};
module.exports = pieRepo;
However when I run "npm start" it throws the below error
/workingdirectory/repos/pieRepo.js:12
resolve(JSON.parse(data));
^
TypeError: resolve is not a function
at /workingdirectory/repos/pieRepo.js:12:17
at FSReqWrap.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:53:3)
I am using version 16.11.0 of node.
The issue you are facing is with the way you are trying to resolve promise. The Resolve & Reject Functions are available within Promise
let fs = require("fs");
const FILE_NAME = "YOUR PATH TO FILE";
let pieRepo = {
get: () => {
return new Promise((resolve, reject) => {
fs.readFile(FILE_NAME, (err, data) => {
if (err) {
return reject(err);
}
resolve(JSON.parse(data));
});
});
},
};
module.exports = pieRepo;
You can further read about Promise
Resolve and reject are functions available in promises.
Replace your code with this:
let fs = require('fs');
const FILE_NAME = './assets/pies.json';
let pieRepo = {
get: () => {
return new Promise((resolve, reject) => {
fs.readFile(FILE_NAME, (err, data) => {
if (err) {
return reject(err);
}
resolve(JSON.parse(data));
});
});
},
};
module.exports = pieRepo;
Now, you can await the get function.
If this were my project though, the code would look like this:
let fs = require('fs/promises');
const FILE_NAME = './assets/pies.json';
let pieRepo = {
get: async () => {
try {
const data = await fs.readFile(FILE_NAME);
return data;
} catch (err) {
throw new Error(err.message);
}
},
};
module.exports = pieRepo;
If you want to promisify fs.readFile, you can, but promisified versions of fs functions are available through fs/promises.
You have to use Promise, here is a very simple example:
test() {
return new Promise((resolve, reject) => {
if (1 === 1) {
resolve(true)
} else {
reject(false)
}
})
}
I was hoping this would be a simple thing, but I cannot find anything out there to do so.
I just want to get all folders/directories within a given folder/directory.
So for example:
<MyFolder>
|- SomeFolder
|- SomeOtherFolder
|- SomeFile.txt
|- SomeOtherFile.txt
|- x-directory
I would expect to get an array of:
["SomeFolder", "SomeOtherFolder", "x-directory"]
Or the above with the path if that was how it was served...
So does anything already exist to do the above?
Promise
import { readdir } from 'fs/promises'
const getDirectories = async source =>
(await readdir(source, { withFileTypes: true }))
.filter(dirent => dirent.isDirectory())
.map(dirent => dirent.name)
Callback
import { readdir } from 'fs'
const getDirectories = (source, callback) =>
readdir(source, { withFileTypes: true }, (err, files) => {
if (err) {
callback(err)
} else {
callback(
files
.filter(dirent => dirent.isDirectory())
.map(dirent => dirent.name)
)
}
})
Syncronous
import { readdirSync } from 'fs'
const getDirectories = source =>
readdirSync(source, { withFileTypes: true })
.filter(dirent => dirent.isDirectory())
.map(dirent => dirent.name)
List directories using a path.
function getDirectories(path) {
return fs.readdirSync(path).filter(function (file) {
return fs.statSync(path+'/'+file).isDirectory();
});
}
Recursive solution
I came here in search of a way to get all of the subdirectories, and all of their subdirectories, etc. Building on the accepted answer, I wrote this:
const fs = require('fs');
const path = require('path');
function flatten(lists) {
return lists.reduce((a, b) => a.concat(b), []);
}
function getDirectories(srcpath) {
return fs.readdirSync(srcpath)
.map(file => path.join(srcpath, file))
.filter(path => fs.statSync(path).isDirectory());
}
function getDirectoriesRecursive(srcpath) {
return [srcpath, ...flatten(getDirectories(srcpath).map(getDirectoriesRecursive))];
}
This should do it:
CoffeeScript (sync)
fs = require 'fs'
getDirs = (rootDir) ->
files = fs.readdirSync(rootDir)
dirs = []
for file in files
if file[0] != '.'
filePath = "#{rootDir}/#{file}"
stat = fs.statSync(filePath)
if stat.isDirectory()
dirs.push(file)
return dirs
CoffeeScript (async)
fs = require 'fs'
getDirs = (rootDir, cb) ->
fs.readdir rootDir, (err, files) ->
dirs = []
for file, index in files
if file[0] != '.'
filePath = "#{rootDir}/#{file}"
fs.stat filePath, (err, stat) ->
if stat.isDirectory()
dirs.push(file)
if files.length == (index + 1)
cb(dirs)
JavaScript (async)
var fs = require('fs');
var getDirs = 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()) {
dirs.push(this.file);
}
if (files.length === (this.index + 1)) {
return cb(dirs);
}
}.bind({index: index, file: file}));
}
}
});
}
Alternatively, if you are able to use external libraries, you can use filehound. It supports callbacks, promises and sync calls.
Using promises:
const Filehound = require('filehound');
Filehound.create()
.path("MyFolder")
.directory() // only search for directories
.find()
.then((subdirectories) => {
console.log(subdirectories);
});
Using callbacks:
const Filehound = require('filehound');
Filehound.create()
.path("MyFolder")
.directory()
.find((err, subdirectories) => {
if (err) return console.error(err);
console.log(subdirectories);
});
Sync call:
const Filehound = require('filehound');
const subdirectories = Filehound.create()
.path("MyFolder")
.directory()
.findSync();
console.log(subdirectories);
For further information (and examples), check out the docs: https://github.com/nspragg/filehound
Disclaimer: I'm the author.
With node.js version >= v10.13.0, fs.readdirSync will return an array of fs.Dirent objects if withFileTypes option is set to true.
So you can use,
const fs = require('fs')
const directories = source => fs.readdirSync(source, {
withFileTypes: true
}).reduce((a, c) => {
c.isDirectory() && a.push(c.name)
return a
}, [])
var getDirectories = (rootdir , cb) => {
fs.readdir(rootdir, (err, files) => {
if(err) throw err ;
var dirs = files.map(filename => path.join(rootdir,filename)).filter( pathname => fs.statSync(pathname).isDirectory());
return cb(dirs);
})
}
getDirectories( myDirectories => console.log(myDirectories));``
Using fs-extra, which promises the async fs calls, and the new await async syntax:
const fs = require("fs-extra");
async function getDirectories(path){
let filesAndDirectories = await fs.readdir(path);
let directories = [];
await Promise.all(
filesAndDirectories.map(name =>{
return fs.stat(path + name)
.then(stat =>{
if(stat.isDirectory()) directories.push(name)
})
})
);
return directories;
}
let directories = await getDirectories("/")
This answer does not use blocking functions like readdirSync or statSync. It does not use external dependencies nor find itself in the depths of callback hell.
Instead we use modern JavaScript conveniences like Promises and and async-await syntaxes. And asynchronous results are processed in parallel; not sequentially -
const { readdir, stat } =
require ("fs") .promises
const { join } =
require ("path")
const dirs = async (path = ".") =>
(await stat (path)) .isDirectory ()
? Promise
.all
( (await readdir (path))
.map (p => dirs (join (path, p)))
)
.then
( results =>
[] .concat (path, ...results)
)
: []
I'll install an example package, and then test our function -
$ npm install ramda
$ node
Let's see it work -
> dirs (".") .then (console.log, console.error)
[ '.'
, 'node_modules'
, 'node_modules/ramda'
, 'node_modules/ramda/dist'
, 'node_modules/ramda/es'
, 'node_modules/ramda/es/internal'
, 'node_modules/ramda/src'
, 'node_modules/ramda/src/internal'
]
Using a generalised module, Parallel, we can simplify the definition of dirs -
const Parallel =
require ("./Parallel")
const dirs = async (path = ".") =>
(await stat (path)) .isDirectory ()
? Parallel (readdir (path))
.flatMap (f => dirs (join (path, f)))
.then (results => [ path, ...results ])
: []
The Parallel module used above was a pattern that was extracted from a set of functions designed to solve a similar problem. For more explanation, see this related Q&A.
And a async version of getDirectories, you need the async module for this:
var fs = require('fs');
var path = require('path');
var async = require('async'); // https://github.com/caolan/async
// Original function
function getDirsSync(srcpath) {
return fs.readdirSync(srcpath).filter(function(file) {
return fs.statSync(path.join(srcpath, file)).isDirectory();
});
}
function getDirs(srcpath, cb) {
fs.readdir(srcpath, function (err, files) {
if(err) {
console.error(err);
return cb([]);
}
var iterator = function (file, cb) {
fs.stat(path.join(srcpath, file), function (err, stats) {
if(err) {
console.error(err);
return cb(false);
}
cb(stats.isDirectory());
})
}
async.filter(files, iterator, cb);
});
}
Fully async version with ES6, only native packages, fs.promises and async/await, does file operations in parallel:
const fs = require('fs');
const path = require('path');
async function listDirectories(rootPath) {
const fileNames = await fs.promises.readdir(rootPath);
const filePaths = fileNames.map(fileName => path.join(rootPath, fileName));
const filePathsAndIsDirectoryFlagsPromises = filePaths.map(async filePath => ({path: filePath, isDirectory: (await fs.promises.stat(filePath)).isDirectory()}))
const filePathsAndIsDirectoryFlags = await Promise.all(filePathsAndIsDirectoryFlagsPromises);
return filePathsAndIsDirectoryFlags.filter(filePathAndIsDirectoryFlag => filePathAndIsDirectoryFlag.isDirectory)
.map(filePathAndIsDirectoryFlag => filePathAndIsDirectoryFlag.path);
}
Tested, it works nicely.
You can use graph-fs
const {Node} = require("graph-fs");
const directory = new Node("/path/to/directory");
const subDirectories = directory.children.filter(child => child.is.directory);
Using the glob package, just add a trailing slash to find directories only:
import {promise as glob} from "glob-promise"
const firstLevelFolders = await glob("MyFolder/*/")
const recursiveFolders = await glob("MyFolder/**/")
CoffeeScript version of this answer, with proper error handling:
fs = require "fs"
{join} = require "path"
async = require "async"
get_subdirs = (root, callback)->
fs.readdir root, (err, files)->
return callback err if err
subdirs = []
async.each files,
(file, callback)->
fs.stat join(root, file), (err, stats)->
return callback err if err
subdirs.push file if stats.isDirectory()
callback null
(err)->
return callback err if err
callback null, subdirs
Depends on async
Alternatively, use a module for this!
(There are modules for everything. [citation needed])
If you need to use all async version. You can have something like this.
Record the directory length, uses it as an indicator to tell if all async stat tasks are finished.
If the async stat tasks are finished, all the file stat has been checked, so call the callback
This will only work as long as Node.js is single thread, because it assumes no two async tasks will increase the counter at the same time.
'use strict';
var fs = require("fs");
var path = require("path");
var basePath = "./";
function result_callback(results) {
results.forEach((obj) => {
console.log("isFile: " + obj.fileName);
console.log("fileName: " + obj.isFile);
});
};
fs.readdir(basePath, (err, files) => {
var results = [];
var total = files.length;
var finished = 0;
files.forEach((fileName) => {
// console.log(fileName);
var fullPath = path.join(basePath, fileName);
fs.stat(fullPath, (err, stat) => {
// this will work because Node.js is single thread
// therefore, the counter will not increment at the same time by two callback
finished++;
if (stat.isFile()) {
results.push({
fileName: fileName,
isFile: stat.isFile()
});
}
if (finished == total) {
result_callback(results);
}
});
});
});
As you can see, this is a "depth first" approach, and this could result in callback hell, and it is not quite "functional" . People try to solve this problem with Promise, by wrapping the async task into an Promise object.
'use strict';
var fs = require("fs");
var path = require("path");
var basePath = "./";
function result_callback(results) {
results.forEach((obj) => {
console.log("isFile: " + obj.fileName);
console.log("fileName: " + obj.isFile);
});
};
fs.readdir(basePath, (err, files) => {
var results = [];
var total = files.length;
var finished = 0;
var promises = files.map((fileName) => {
// console.log(fileName);
var fullPath = path.join(basePath, fileName);
return new Promise((resolve, reject) => {
// try to replace fullPath wil "aaa", it will reject
fs.stat(fullPath, (err, stat) => {
if (err) {
reject(err);
return;
}
var obj = {
fileName: fileName,
isFile: stat.isFile()
};
resolve(obj);
});
});
});
Promise.all(promises).then((values) => {
console.log("All the promise resolved");
console.log(values);
console.log("Filter out folder: ");
values
.filter((obj) => obj.isFile)
.forEach((obj) => {
console.log(obj.fileName);
});
}, (reason) => {
console.log("Not all the promise resolved");
console.log(reason);
});
});
use fs、path module can got the folder. this use Promise. If your will get the fill, your can change isDirectory() to isFile() Nodejs--fs--fs.Stats.At last, you can get the file'name file'extname and so on Nodejs---Path
var fs = require("fs"),
path = require("path");
//your <MyFolder> path
var p = "MyFolder"
fs.readdir(p, function (err, files) {
if (err) {
throw err;
}
//this can get all folder and file under <MyFolder>
files.map(function (file) {
//return file or folder path, such as **MyFolder/SomeFile.txt**
return path.join(p, file);
}).filter(function (file) {
//use sync judge method. The file will add next files array if the file is directory, or not.
return fs.statSync(file).isDirectory();
}).forEach(function (files) {
//The files is array, so each. files is the folder name. can handle the folder.
console.log("%s", files);
});
});
Just in case anyone else ends up here from a web search, and has Grunt already in their dependency list, the answer to this becomes trivial. Here's my solution:
/**
* Return all the subfolders of this path
* #param {String} parentFolderPath - valid folder path
* #param {String} glob ['/*'] - optional glob so you can do recursive if you want
* #returns {String[]} subfolder paths
*/
getSubfolders = (parentFolderPath, glob = '/*') => {
return grunt.file.expand({filter: 'isDirectory'}, parentFolderPath + glob);
}
Another recursive approach
Thanks to Mayur for knowing me about withFileTypes. I written following code for getting files of particular folder recursively. It can be easily modified to get only directories.
const getFiles = (dir, base = '') => readdirSync(dir, {withFileTypes: true}).reduce((files, file) => {
const filePath = path.join(dir, file.name)
const relativePath = path.join(base, file.name)
if(file.isDirectory()) {
return files.concat(getFiles(filePath, relativePath))
} else if(file.isFile()) {
file.__fullPath = filePath
file.__relateivePath = relativePath
return files.concat(file)
}
}, [])
functional programming
const fs = require('fs')
const path = require('path')
const R = require('ramda')
const getDirectories = pathName => {
const isDirectory = pathName => fs.lstatSync(pathName).isDirectory()
const mapDirectories = pathName => R.map(name => path.join(pathName, name), fs.readdirSync(pathName))
const filterDirectories = listPaths => R.filter(isDirectory, listPaths)
return {
paths:R.pipe(mapDirectories)(pathName),
pathsFiltered: R.pipe(mapDirectories, filterDirectories)(pathName)
}
}
You could use dree, if using a module is affordable
const dree = require('dree');
const options = {
depth: 1
};
const fileCallback = function() {};
const directories = [];
const dirCallback = function(dir) {
directories.push(dir.name);
};
dree.scan('./dir', {});
console.log(directories);
The directories which are directed children of the specified path ("./dir") will be printed.
If you do not put the option depth: 1, you would even obtain all the directories in a recursively way, so not only the directed children of the specified path.
I have an script to looping over directories and match files with specific type. Unfortunately jest passes this test before it ends. I know why, but I don't know how to make script to wait for the end of looping.
import fs from 'fs'
const path = require('path');
describe('something', () => {
it('should something', () => {
const traverseDir = (dir, callback) => {
fs.readdirSync(dir).forEach(file => {
let fullPath = path.join(dir, file);
if (fs.lstatSync(fullPath).isDirectory()) {
callback(fullPath)
traverseDir(fullPath, callback);
} else {
callback(fullPath)
}
});
}
traverseDir('src/', (fullPath) => {
const splitted = fullPath.split('/')
const filename = splitted[splitted.length - 1]
if (filename.match(/.*.foo/)) {
fs.readFile(fullPath, 'utf8', (err, data) => {
expect(err).toBe(null)
// some assertion
})
}
})
})
})
You could pass done in the test parameter and call it when the test ends.
You can read more about async testing here.
import fs from "fs";
const path = require("path");
describe("something", () => {
it("should something", done => {
const traverseDir = (dir, callback) => {
fs.readdirSync(dir).forEach(file => {
let fullPath = path.join(dir, file);
if (fs.lstatSync(fullPath).isDirectory()) {
callback(fullPath);
traverseDir(fullPath, callback);
} else {
callback(fullPath);
}
});
done(); // Call done to tell Jest that the test has finished.
};
traverseDir("src/", fullPath => {
const splitted = fullPath.split("/");
const filename = splitted[splitted.length - 1];
if (filename.match(/.*.foo/)) {
fs.readFile(fullPath, "utf8", (err, data) => {
expect(err).toBe(null);
});
}
});
});
});
You should use fs.promises functions to list the contents of your directory recursively to obtain a single unified file list.
Unit test this function separately from any code that actually reads the file. (e.g.: your filename.match and readFile code should be tested separately from the traverseDir code.)
Example of walking directories asynchronously to get a unified file list:
This asynchronous allFilesIn function gets all files within a directory recursively and returns the list as a single array with full (relative) paths.
const fs = require('fs').promises;
const path = require('path');
const allFilesIn = async (dir, results = []) => {
const files = await fs.readdir(dir);
for (file of files) {
const fullPath = path.join(dir, file);
const stat = await fs.stat(fullPath);
if (stat.isDirectory()) {
await allFilesIn(fullPath, results);
} else {
results.push(fullPath);
}
}
return results;
}
// Example call:
allFilesIn('src/').then(files => {
console.log(files); // e.g.: [ 'src\\foo.cpp', 'src\\bar.cpp', 'src\\include\\foo.h' ]
});
Once you have a single array of all the files it should be easy to use a single forEach to do something for all the files in the unified list.
Is there a faster or more succinct way to concatenate all of the files located in a directory using NodeJS?
In bash I could do something like this:
for file in $1
do
cat "$file"
echo
done > $2;
Here is what I'm doing now:
var fs = require('fs');
var Promise = require('bluebird');
module.exports = function(directory, destination) {
return new Promise((resolve, reject) => {
fs.readdir(directory, (err, files) => {
if (err) {
return reject(err);
}
(function next() {
var file = files.shift();
if (!file) {
return resolve();
}
fs.readFile(directory + '/' + file, (err, content) => {
if (err) {
return reject(err);
}
fs.appendFile(destination, '\n' + content, (err) => {
if (err) {
return reject(err);
}
return next();
});
});
})();
});
});
};
That ?
require('child_process').execSync('cat *').toString('UTF-8')
:D
Using the async library you can easily read files in parallel and then join the results.
const fs = require("fs");
const async = require("async");
const path = require("path");
module.exports = function(directory, destination) {
return new Promise((resolve, reject) => {
fs.readdir(directory, (err, files) => {
if (err)
return reject(err);
files = files.map(file => path.join(directory,file));
//Read all files in parallel
async.map(files, fs.readFile, (err, results) => {
if (err)
return reject(err);
//results[0] contents of file #1
//results[1] contents of file #2
//results[n] ...
//Write the joined results to destination
fs.writeFile(destination, results.join("\n"), (err) => {
if (err)
return reject(err);
resolve();
});
});
});
});
}
If you're going to use bluebird than you get the benefit of promisification. You can use promisifyAll() to convert all error first callback accepting async functions in the fs module to return a promise. You can read more about in the above promisification link.
The below code reads in all of the files as strings and then reduces all of their contents into a single string and writes that string to the destination.
Its probably best to not catch() any returned errors here. Rather, the caller should attach a catch() to handle any returned errors as they need.
const Promise = require('bluebird')
const fs = Promise.promisifyAll(require('fs'))
const path = require('path')
module.exports = (directory, destination) => {
return fs.readdirAsync(directory)
.map(file => fs.readFileAsync(path.join(directory, file), 'utf8'))
.then(contents => fs.writeFileAsync(destination, contents.join('\n')))
}
All in one line:
fs.readdirSync('./').forEach((file) => { if(fs.lstatSync(file).isFile()) fs.appendFileSync('./output.file', fs.readFileSync(file).toString()) })
Replace './' with target directory and './output.file' with target destination.
You can do the same thing without bluebird , since node 8.X includes the util package to promisify fs API.
This exemple shows how i use it in my project to concatenate minified files (so remove the filter if necessary).
You can do the same thing without bluebird , since node 8.X includes the util package to promisify fs API.
This exemple shows how i use it in my project to concatenate minified files (so remove the filter if necessary).
const {promisify} = require("util"); //requires node 8.X
const readdir = promisify(fs.readdir);
const readFile = promisify(fs.readFile);
const appendFile = promisify(fs.appendFile);
// Append all minified and obsfucated files in source directory
// The resulting file is generated in destination
function appendFile(directory, destination) {
readdir(directory)
.then((files) => {
console.log('FILES CONTENT:', files);
files.filter(file => {
console.log('FILTER > ' + file);
return (file.indexOf('-min.js') != -1 && file.indexOf('-min.js.map') == -1)
})
.map(file => {
console.log('MAP ('+destination+') > ' + path.join(directory, file));
readFile(path.join(directory, file), 'utf8')
.then(data => {
//console.log('DATA:', data);
appendFile(destination, data+'\n')
.then(() => {
console.log('append done');
})
.catch((err) => {
displayError(err);
});
});
});
})
.catch((err) => {
console.log('ERROR:', err);
displayError(err);
});
}