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?

var dirname = 'C:/FolderwithFiles'; console.log("Going to get file info!"); fs.stat(dirname, function (err, stats) {     if (err) {         return console.error(err);     }     console.log(stats);     console.log("Got file info successfully!");      // Check file type     console.log("isFile ? " + stats.isFile());     console.log("isDirectory ? " + stats.isDirectory()); }); 

Answer 1

Older answer with callbacks

You want to use the fs.readdir function to get the directory contents and the fs.rename function to actually do the renaming. Both these functions have synchronous versions if you need to wait for them to finishing before running the code afterwards.

I wrote a quick script that does what you described.

var fs = require('fs'); var path = require('path'); // In newer Node.js versions where process is already global this isn't necessary. var process = require("process");  var moveFrom = "/home/mike/dev/node/sonar/moveme"; var moveTo = "/home/mike/dev/node/sonar/tome"  // Loop through all the files in the temp directory fs.readdir(moveFrom, function (err, files) {   if (err) {     console.error("Could not list the directory.", err);     process.exit(1);   }    files.forEach(function (file, index) {     // Make one pass and make the file complete     var fromPath = path.join(moveFrom, file);     var toPath = path.join(moveTo, file);      fs.stat(fromPath, function (error, stat) {       if (error) {         console.error("Error stating file.", error);         return;       }        if (stat.isFile())         console.log("'%s' is a file.", fromPath);       else if (stat.isDirectory())         console.log("'%s' is a directory.", fromPath);        fs.rename(fromPath, toPath, function (error) {         if (error) {           console.error("File moving error.", error);         } else {           console.log("Moved file '%s' to '%s'.", fromPath, toPath);         }       });     });   }); }); 

Tested on my local machine.

node testme.js  '/home/mike/dev/node/sonar/moveme/hello' is a file. '/home/mike/dev/node/sonar/moveme/test' is a directory. '/home/mike/dev/node/sonar/moveme/test2' is a directory. '/home/mike/dev/node/sonar/moveme/test23' is a directory. '/home/mike/dev/node/sonar/moveme/test234' is a directory. Moved file '/home/mike/dev/node/sonar/moveme/hello' to '/home/mike/dev/node/sonar/tome/hello'. Moved file '/home/mike/dev/node/sonar/moveme/test' to '/home/mike/dev/node/sonar/tome/test'. Moved file '/home/mike/dev/node/sonar/moveme/test2' to '/home/mike/dev/node/sonar/tome/test2'. Moved file '/home/mike/dev/node/sonar/moveme/test23' to '/home/mike/dev/node/sonar/tome/test23'. Moved file '/home/mike/dev/node/sonar/moveme/test234' to '/home/mike/dev/node/sonar/tome/test234'. 

Update: fs.promises functions with async/await

Inspired by ma11hew28's answer (shown here), here is the same thing as above but with the async functions in fs.promises. As noted by ma11hew28, this may have memory limitations versus fs.promises.opendir added in v12.12.0.

Quick code below.

//jshint esversion:8 //jshint node:true const fs = require( 'fs' ); const path = require( 'path' );  const moveFrom = "/tmp/movefrom"; const moveTo = "/tmp/moveto";  // Make an async function that gets executed immediately (async ()=>{     // Our starting point     try {         // Get the files as an array         const files = await fs.promises.readdir( moveFrom );          // Loop them all with the new for...of         for( const file of files ) {             // Get the full paths             const fromPath = path.join( moveFrom, file );             const toPath = path.join( moveTo, file );              // Stat the file to see if we have a file or dir             const stat = await fs.promises.stat( fromPath );              if( stat.isFile() )                 console.log( "'%s' is a file.", fromPath );             else if( stat.isDirectory() )                 console.log( "'%s' is a directory.", fromPath );              // Now move async             await fs.promises.rename( fromPath, toPath );              // Log because we're crazy             console.log( "Moved '%s'->'%s'", fromPath, toPath );         } // End for...of     }     catch( e ) {         // Catch anything bad that happens         console.error( "We've thrown! Whoops!", e );     }  })(); // Wrap in parenthesis and call now 

Answer 2

fs.readdir(path[, options], callback) (which Mikey A. Leonetti used in his answer) and its variants (fsPromises.readdir(path[, options]) and fs.readdirSync(path[, options])) each reads all of a directory's entries into memory at once. That's good for most cases, but if the directory has very many entries and/or you want to lower your application's memory footprint, you could instead iterate over the directory's entries one at a time.

Asynchronously

Directories are async iterable, so you could do something like this:

const fs = require('fs')  async function ls(path) {   const dir = await fs.promises.opendir(path)   for await (const dirent of dir) {     console.log(dirent.name)   } }  ls('.').catch(console.error) 

Or, you could use dir.read() and/or dir.read(callback) directly.

Synchronously

Directories aren't sync iterable, but you could use dir.readSync() directly. For example:

const fs = require('fs')  const dir = fs.opendirSync('.') let dirent while ((dirent = dir.readSync()) !== null) {   console.log(dirent.name) } dir.closeSync() 

Or, you could make directories sync iterable. For example:

const fs = require('fs')  function makeDirectoriesSyncIterable() {   const p = fs.Dir.prototype   if (p.hasOwnProperty(Symbol.iterator)) { return }   const entriesSync = function* () {     try {       let dirent       while ((dirent = this.readSync()) !== null) { yield dirent }     } finally { this.closeSync() }   }   if (!p.hasOwnProperty(entriesSync)) { p.entriesSync = entriesSync }   Object.defineProperty(p, Symbol.iterator, {     configurable: true,     enumerable: false,     value: entriesSync,     writable: true   }) } makeDirectoriesSyncIterable() 

And then, you could do something like this:

const dir = fs.opendirSync('.') for (const dirent of dir) {   console.log(dirent.name) } 

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Note: "In busy processes, use the asynchronous versions of these calls. The synchronous versions will block the entire process until they complete, halting all connections."

References:

• Node.js Documentation: File System: Class fs.Dir
• Node.js source code: fs.Dir
• GitHub: nodejs/node: Issues: streaming / iterative fs.readdir #583