- Create and Add data in a File
- Rename file
- Delete file
- fs-extra module
The Node.js file system module (fs) allows you to work with files and folders on your server.
Use this code to include the "fs" module:
const fs = require('fs');
Read File
To read a file on your server, you can use the fs.readFile() method.Example: Assume we have the following HTML file, called "file1.htm" (located in a "test/" folder, in the Node.js directory):
<html> <body> <h1>H1 Title Header</h1> <p>Some text content.</p> </body> </html>Create a Node.js file that reads the HTML file, and return the content:
//include http and fs modules
const http = require('http');
const fs = require('fs');
//path and file name to read
let file ='./test/file1.htm';
//sets server
const server = http.createServer((req, res)=>{
//reads the file; if no error, output its content
fs.readFile(file, (err, data)=>{
if(err) throw err;
else {
res.writeHead(200, {'Content-Type': 'text/html'});
res.write(data);
}
res.end();
});
});
//listens the server on port 8080
server.listen(8080, ()=> {
console.log('Server running at //localhost:8080/');
});
Save the code above in a file called "readfile1.js", and initiate the file in command line interface. Then, access the server in your browser: "//localhost:8080/".- In browser will appear a page with the content of the "file1.htm" file.
Get File Information
To get the information about a file, use the fs.stat() method.Example: Get object with information about "file1.htm":
const fs = require('fs');
var file ='./test/file1.htm';
fs.stat(file, (err, stats)=>{
if(err) throw err;
console.log(stats);
// Check file type
console.log('isFile ? '+ stats.isFile());
});
If you save the code above in a Node.js file, for example called "fileinfo.js" and run the file in command line interface, you'll get a result like in this screenshoot:
- The stats parameter of the callback function is an object with file information (mode, size, etc.); also, it has methods which can be used to check file type.
stats.isFile() - Returns true if file type of a simple file.
stats.isDirectory() - Returns true if file type of a directory.
stats.isBlockDevice() - Returns true if file type of a block device.
Create and Add data in a File
The "fs" module has methods for creating new files, or adding data in existing file:- fs.appendFile()
- fs.open()
- fs.writeFile()
- Example: Create a html file using the appendFile() method:
const fs = require('fs');
var file ='./test/newfile.htm';
var content ='<div>Html content</div>';
fs.appendFile(file, content, (err)=>{
if(err) throw err;
console.log('Saved.');
});
If you save the code above in a Node.js file, and initiate it in the command line interface, a new file "newfile.htm" will be created in "test/" folder (located in the same directory as the Node.js application).2. The fs.open() method takes a "flag" as the second argument, if the flag is "w" for "writing", the specified file is opened for writing. If the file does not exist, an empty file is created.
- The fs.open() method can be used to create, read, write a file, depending on the specified flag (r, r+, a, w, w+, etc.). See fs.open() documentation page.
- Example: Create a html file using the fs.open() method, and add content in the opened file using fs.write() method:
const fs = require('fs');
var file ='./test/newfile.htm';
var content ='<div>Html content</div>';
fs.open(file, 'w', (err, fd)=>{
if(err) throw err;
else {
console.log('File created');
fs.write(fd, content, (err)=>{
if(err) throw err;
console.log('Data added in file');
fs.close(fd, (err)=>{ if(err) throw err;});
});
}
});
3. The fs.writeFile() method replaces the specified file and content if it exists. If the file does not exists a new file, containing the specified content, will be created.
- Example: Create a new file using the writeFile() method:
const fs = require('fs');
var file ='./test/newfile.htm';
var content ='<div>Html content</div>';
fs.writeFile(file, content, (err)=>{
if(err) throw err;
console.log('Saved.');
});
Rename file
To rename a file with the File System module, use the fs.rename() method.Example: Rename "newfile.htm" to "renamedfile.htm":
const fs = require('fs');
var file ='./test/newfile.htm';
var newname ='./test/renamedfile.htm';
fs.rename(file, newname, (err)=>{
if(err) throw err;
else console.log('Renamed.');
});
Delete file
To delete a file with the File System module, use the fs.unlink() method.Example: Delete "filename.htm" from "test/" folder:
const fs = require('fs');
var file ='./test/filename.htm';
fs.unlink(file, (err)=>{
if(err) throw err;
else console.log('Deleted.');
});
fs-extra module
Another option to easily work with directories and files on server, use the fs-extra module.fs-extra adds file system methods that aren't included in the native "fs" module and adds promise support to the "fs" methods. It can be a drop in replacement for "fs".
- Before using the "fs-extra" module, you have to install it. To install "fs-extra", run this code in command line interface:
npm install --save fs-extraThen, you can use the fs-extra module in your Node.js projects, as a drop in replacement for native fs.
const fs = require('fs-extra');
All methods in fs are attached to fs-extra. All fs methods return promises if the callback isn't passed.Example:
const fs = require('fs-extra')
// Async with promises:
fs.copy('/tmp/file.htm', '/tmp/dirx/file.htm')
.then(() => console.log('success!'))
.catch(err => console.error(err));
// Async with callbacks:
fs.copy('/tmp/file.htm', '/tmp/dirx/file.htm', err =>{
if (err) return console.error(err);
console.log('success!');
});
// Sync:
try {
fs.copySync('/tmp/file.htm', '/tmp/dirx/file.htm');
console.log('success!');
} catch (err){
console.error(err);
}
- For documentation, see the fs-extra module page
