Table of Contents
1. What module fs?
2. Read file with module fs
3. Write file with module js
1. What module fs?
Module fs (short for file system) is a module built in node.js that handles files, folders in node.js
Syntax
var fs = require(‘fs’);
2. Read file with module fs
Syntax
readFile(‘pathFile’, [option], function(err, data){
//
});
Parameters
+ pathFile is the path of the file to be read.
+ option: can be a string or an array containing the option to encode or mode the file, if no configuration is needed, everyone can leave it blank.
+ err: is the variable containing the error if any.
+ data: is data read from the file.
Example
First, let us a js file named hello.html having the following code:
<!DOCTYPE html>
<html>
<head>
<meta charset=”utf-8″>
<meta http-equiv=”X-UA-Compatible” content=”IE=edge”>
<title>toidicode.com</title>
<link rel=”stylesheet” href=””>
</head>
<style type=”text/css” media=”screen”>
h1{
color: orange;
text-align: center;
}
</style>
<body>
<h1>Welcome to My blog!</h1>
</body>
</html>
Next, we need create a file unit8.js to initialize the server and process the file
var http = require(‘http’);
var fs = require(‘fs’);
http.createServer(function(request, response){
response.writeHead(‘200’, {‘content-type’: ‘text/html’});
fs.readFile(‘hello.html’, ‘utf8’, function(err, data){
if (err) throw err;
response.write(data);
response.end();
})
}).listen(8081);
Then you run: node unit8.js and will get the following results:
Welcome to My blog!
3. Write file with module js
Syntax
Following is the syntax of one of the methods to write into a file
fs.
fs.writeFile(filename, data[options], callback)
This method will over-write the file if the file already exists. If you want to write into an existing file then you should use another method available.
Parameters
+ path: This is the string having the file name including path.
+ data: This is the String or Buffer to be written into the file.
+ options: The third parameter is an object which will hold {encoding, mode, flag}. By default, encoding is utf8, mode is octal value 0666, and flag is ‘w’.
+ callback: This is the callback function which gets a single parameter err that returns an error in case of any writing error.
Example
var fs = require(‘fs’);
console.log(“Going to write into existing file”);
fs.writeFile(‘files/hello.txt’, ‘Simply easy learing!’, function(err){
if (err) {
return console.error(err);
}
console.log(‘Data written successfully!’);
fs.readFile(‘files/hello.txt’, function (err, data){
if (err) {
return console.error(err);
}
console.log(‘Data of file: ‘ + data.toString());
});
});
Now run the unit8.js to see the result:
$ node unit8.js
Verify the output:
Going to write into existing file
Data written successfully!
Data of file: Simply easy learing!
Thank you for reading!
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