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

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.

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[angphu]

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 !!!

[shivendrasrivastava]

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.

[rucklerful]

Awesome, finlay understood syncronous and asyncronous.

[escapefelicity]

Great job. I learned more from this than I had in the preceding 3 hours.

[MrToPi]

I like the way you go through all the stuff, helps me understand better

[IslanKleinknecht]

I hope you'll be talking about database access with Node JS.

[prateekcool]

Wow! Finally able to understand synchronous and asynchronous.
Thanks a ton man!

[ayseak_]

The best way to learn Node JS is to watch your video series and read comments below of each video) Thanks)

[georgephillips]

if anyone gets the "TypeError [ERR_INVALID_CALLBACK]: Callback must be a function" error just add ()=>{} as a third argument to the writeFile function to fix it

[SilvestreVivo]

Finally a very good node.js tutorial!! You're very good, man!

[johnsonlai]

Got this warning from node:
DeprecationWarning: Calling an asynchronous function without callback is deprecated.

I replaced

fs.writeFile("writeMe.txt", data);

with

fs.writeFile('writeMe.txt', data, (err) => {
if (err) throw err;
console.log('It is saved!');
});

Hope it helps.

[JonathanSueck]

You didn't destroy my eardrums in this video, THANK YOU

[nahfamimgood]

episodes like this is when my brain starts running about thinking of all the awesome things you can do with this...

[matheussanchez]

this is probably the best tutorial i've ever seen

[shihabmunshi]

thank you so much, even in 2022 its very useful

[tomaszkonecki]

Things are starting to clear up in my head. Another great tutorial.

[mzamomahaeng]

Excellent video and so well explained 👏 👍 👌 😀 thanks so much

[vilmiswow]

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

[muhammadsafiullah]

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

[PixiiBomb]

@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