Node JS Tutorial for Beginners #9 – Reading & Writing Files (fs)

45
7



Yo ninjas, in this Node JS tutorial, I’ll go through how we can use the ‘fs’ module in node to go out and read & write files to our computer.

—– COURSE LINKS:
+ Repo –
+ Atom editor –

———————————————————————————————
You can find more front-end development tutorials on CSS, HTML, JavaScript, jQuery, WordPress & more on the channel homepage…

SUBSCRIBE TO CHANNEL –

========== JavaScript for Beginners Playlist ==========

============ CSS for Beginners Playlist =============

============== The Net Ninja =====================

For more front-end development tutorials & to black-belt your coding skills, head over to – or

================== Social Links ==================

Twitter – @TheNetNinja –

Nguồn: https://canhosafira.com.vn

Xem thêm bài viết khác: https://canhosafira.com.vn/cong-nghe

45 COMMENTS

  1. does this method of using async work with the latest version of node js because idk it's not working for me the same command.help!!!!

  2. New Node version solution
    const fs = require('fs')

    fs.readFile('readMe.txt','utf8', (err, data) => {

    fs.writeFile('writesMe.txt', data,(err,result) => {

    if(err){

    console.log(err);

    }

    })

    })

  3. Hey if anyone stuck upon the error like- call back must be function, then below is the given link go check it out.
    https://stackoverflow.com/questions/51150956/how-to-fix-this-error-typeerror-err-invalid-callback-callback-must-be-a-funct

  4. Any idea for this error? TIA
    fs.js:143
    throw new ERR_INVALID_CALLBACK(cb);
    ^
    this is what my code following your example look like:
    var fs = require('fs');

    fs.readFile('readme.txt','utf8', function(err, data){
    fs.writeFile('writeme.txt', data)

    }); /*I have filenames in smallcaps*/

  5. I understand everything you coded but in JavaScript we pass the arguments in function but in callback mentioned above function (err, data) {….. }
    Where does the values for err, data comes from can you clear my doubt sir

  6. For the last segment
    fs.writeFile('writeme.txt', data, function (err, _data){});

    As writeFile is asynchronous you have to define a callback function , doesn't matter if it's empty, it will still run with no syntax error and get the job done.
    Or you can simply use writeFileSync()
    Hope this helps everyone.

  7. I showed this video to the interviewer and I'm the CEO of that company now. Thanks for sharing this amazing tutorial with us.

  8. @8:40 – If you got an error like ERR_INVALID_CALLBACK: Callback must be a function
    (possibly depreciation since 2016?)

    This is referring to fs.writeFile(yourfilename, yourdata);
    You can try to use:
    async-function{ sync-function }
    or
    async-function{ async-function }

    Example1: async-function{ sync-function }
    fs.readFile('./readme.txt', 'utf8', function(err, data){
    fs.writeFileSync('writeme.txt', data);
    });

    Example2: async-function{ async-function }
    fs.readFile('./readme.txt', 'utf8', function(err, data){
    fs.writeFile('writeme.txt', data, function(err2, data2){
    console.log('Use this method if you want another callback function after you read the file, then write to a new file');
    });
    });

    You can also throw in a "dummy" function. The error requests a callback, but you don't want it to do anything:
    fs.readFile('readme.txt','utf8',function(err,data) {
    fs.writeFile('writeme.txt', data, function());
    })

    There are probably a couple of other options, but these just popped into my head

  9. I don't know why fs module doesn't found my .txt file at the same folder. I need to concat the __dirname with '/readme.txt' string, so it's can run properly

  10. Now if we only use fs.writeFile('file.txt',data) it won't work, we have to use callback function after data like this: fs.writeFile('file.txt,data, (err)=>{ }) so that it will be worked !!!

  11. Who knows what is wrong with this code:

    let events = require("events");

    let util = require("util");

    let Person = (name) => {

    this.name = name;

    };

    util.inherits(Person, events.EventEmitter);

    let james = new Person('james');

    let mary = new Person('mary');

    let ruy = new Person('ruy');

    let people = [james, mary, ruy];

    people.forEach(person => {

    person.on('speak', msg => {

    console.log(person.name + ' said : ' + msg);

    });

    });

    james.emit('speak', 'hey dudes');

    Everything is identical as in video. Can it be because I use a newer version of Node JS?

  12. My god. Java programmer here . I wanted to table flip after I saw how easy it is to readfiles in Node js and I believe this feeling of how easy it is will come back again and again:D

  13. Good day sir. I always have an error with the 'fs.writeFile' but it works on 'fs.writeFileSync' and it also works on 'fs.readFile' . what do you think is my problem sir? thank you for answering. more power. Godbless.

    P.S: this is a great Node Js tutorial .

  14. Noted:

    The asynchronous function always needs a callback function
    Ninja code:
    fs.readFile('readMe.txt', 'utf-8', function(err, data){

    fs.writeFile('writeMe.txt', data);
    });

    But, I will get the below errror:
    TypeError [ERR_INVALID_CALLBACK]: Callback must be a function

    My code:
    fs.readFile('readMe.txt', 'utf-8', function(err, data){

    fs.writeFile('writeMe.txt', data, function(err, result){

    if(err) console.log('error', err);

    });

    });

    This will only works and hope can help you guys.

  15. if you encounter an error said "Callback must be a function", add a function as the last parameter of fs.writeFiles() method.

    For example:

    const fs = require('fs');
    fs.readFile('readme.txt', 'utf8', function(err, data) {
    fs.writeFile('writeme.txt', data, function(){});
    });

    Or, if you want to keep it clear and simple, use this one:

    const fs = require('fs');
    fs.readFile('readme.txt', 'utf8', function(err, data) {
    fs.writeFile('writeme.txt', data, ()=>{});
    });

  16. you have to add err callback function for WriteFile otherwise it is givng error.

    var fs = require('fs');

    fs.readFile('readMe.txt','utf8', function(err,data){

    console.log('read complete');

    fs.writeFile('writeMe.txt',data, function(err){

    console.log('write complete');

    });

    });

  17. fs.readFile('readMe.txt', 'utf8', function (err, data)
    {

    fs.writeFile('writeMe.txt', data, function(err, result)
    {

    if(err) console.log('error', err);

    });

    });

    correct code for async method of writing a file !!

  18. New version of nodeJS requires a callback function in async methods..

    var fs = require('fs');

    fs.readFile('readme.txt','utf8', function(err, data){

    fs.writeFile('writeme.txt',data,function(err){

    if(err)

    console.log(err);

    });

    });

  19. Hi, thanks for this video and others. Just one thing (maybe more for the others): now writeFile does not work without a callback function. Node.js returns ERR_INVALID_CALLBACK error. The definition of a callback seems mandatory.

LEAVE A REPLY

Please enter your comment!
Please enter your name here