The Node.js file system module allows you to work with the file system on your computer.
To include the File System module, use the require() method:
var fs = require('fs');
Common use for the File System module:
Read files
Create files
Update files
Delete files
Rename files
The fs.readFile() method is used to read files on your computer.
Assume we have the following HTML file (located in the same folder as Node.js):
demofile1.html
<html>
<body>
<h1>My Header</h1>
<p>My paragraph.</p>
</body>
</html>
Create a Node.js file that reads the HTML file, and return the content:
var http = require('http');
var fs = require('fs');
http.createServer(function (req, res) {
fs.readFile('demofile1.html', function(err, data) {
res.writeHead(200, {'Content-Type': 'text/html'});
res.write(data);
return res.end();
});
}).listen(8080);
Save the code above in a file called "demo_readfile.js", and initiate the file:
Initiate demo_readfile.js:
C:\Users\Your Name>node demo_readfile.js
If you have followed the same steps on your computer, you will see the same result as the example: http://localhost:8080
The File System module has methods for creating new files:
fs.appendFile()
fs.open()
fs.writeFile()
The fs.appendFile() method appends specified content to a file. If the file does not exist, the file will be created:
Create a new file using the appendFile() method:
var fs = require('fs');
fs.appendFile('mynewfile1.txt', 'Hello content!', function (err) {
if (err) throw err;
console.log('Saved!');
});
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:
Create a new, empty file using the open() method:
var fs = require('fs');
fs.open('mynewfile2.txt', 'w', function (err, file) {
if (err) throw err;
console.log('Saved!');
});
The fs.writeFile() method replaces the specified file and content if it exists. If the file does not exist, a new file, containing the specified content, will be created:
Create a new file using the writeFile() method:
var fs = require('fs');
fs.writeFile('mynewfile3.txt', 'Hello content!', function (err) {
if (err) throw err;
console.log('Saved!');
});
The File System module has methods for updating files:
fs.appendFile()
fs.writeFile()
The fs.appendFile() method appends the specified content at the end of the specified file:
Append "This is my text." to the end of the file "mynewfile1.txt":
var fs = require('fs');
fs.appendFile('mynewfile1.txt', ' This is my text.', function (err) {
if (err) throw err;
console.log('Updated!');
});
The fs.writeFile() method replaces the specified file and content:
Replace the content of the file "mynewfile3.txt":
var fs = require('fs');
fs.writeFile('mynewfile3.txt', 'This is my text', function (err) {
if (err) throw err;
console.log('Replaced!');
});
To delete a file with the File System module, use the fs.unlink() method.
The fs.unlink() method deletes the specified file:
Delete "mynewfile2.txt":
var fs = require('fs');
fs.unlink('mynewfile2.txt', function (err) {
if (err) throw err;
console.log('File deleted!');
});
To rename a file with the File System module, use the fs.rename() method.
The fs.rename() method renames the specified file:
Rename "mynewfile1.txt" to "myrenamedfile.txt":
var fs = require('fs');
fs.rename('mynewfile1.txt', 'myrenamedfile.txt', function (err) {
if (err) throw err;
console.log('File Renamed!');
});