Node.js File System Module
Thursday 28 June 2018
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Node.js as a File Server
The Node.js file system module allow 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
Read 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:
Example
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);
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
Create Files
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:Example
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:Example
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:Example
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!');
});
Update Files
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:Example
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:Example
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!');
});
Delete Files
To delete a file with the File System module, use the
fs.unlink() method.
The
fs.unlink() method deletes the specified file:Example
Delete "mynewfile2.txt":
var fs = require('fs');
fs.unlink('mynewfile2.txt', function (err) {
if (err) throw err;
console.log('File deleted!');
});
Rename Files
To rename a file with the File System module, use the
fs.rename() method.
The
fs.rename() method renames the specified file:Example
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!');
});
Upload Files
You can also use Node.js to upload files to your computer.
Read how in our Node.js Upload Files chapter.
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