File Handling

NodeJS

• file writing
• file reading
• file appending

File Writing

• create app.js in a folder.
• require module called ‘fs’

module name = ‘fs’

fs.writeFile(file path, data, callback)

• file path -> note.txt
• data -> ‘Hello NodeJS’

//app.js

const fs = require('fs');
fs.writeFile('note.txt', 'Hello  NodeJS', (err) => {
    if(!err){
        console.log('successful')
    }else{
        console.log(err);
    }
})

Run app.js with the command

$ node app.js

You will see a new file called note.txt with the text ‘Hello NodeJS’ .

File Reading

fs.readFile(file path, options, callback)

• file path -> note.txt
• options -> ‘utf-8’ (option that we gonna read the file)

//app.js

const fs = require('fs');
fs.readFile('note.txt', 'utf-8', (err, data) => {
    if(!err){
        console.log(data)
    }else{
        console.log(err)
    }
})

Run app.js with the command. You will see the data that we have written.

$ node app
Hello  NodeJS

File Appending

• fs.writeFile search the file that match with name of file in the parameter. If no match file create new file and write data that we pass as a parameter. If there is same file , delete all data in there and replace with the data that we currently pass in.
• fs.appendFile is append the data in a exist file.

fs.appendFile(file path, data, callback)

• file path -> note.txt
• data-> ‘Hello User!’

//app.js

const fs = require('fs');
fs.appendFile('note.txt', 'Hello User!', (err) => {
    if(!err){
        console.log('successful');
    }else{
        console.log(err)
    }
})

Run app.js with the command

$ node app.js

You will see a new file called note.txt as follow

Hello  NodeJSHello User!