Reading and Writing Files with Node.js | Node JS Beginners Tutorial
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- เผยแพร่เมื่อ 6 ก.ค. 2024
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Reading and writing files with Node.js is easy after you learn the Node JS file system module. In this Node beginners tutorial, you will learn how to read, write, update and delete files with Node.js. You will also learn how to create readable and writeable streams of data with Node.
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🚀 This lesson is part of a Node.js for Beginners tutorial series playlist:
• Node.js Tutorials for ...
Reading and Writing Files with Node.js | Node JS File System Tutorial
(00:00) Intro
(00:05) Welcome
(00:15) Overview
(00:33) Use the NodeJS docs
(01:50) How to read a file with Node.js
(03:53) How to handle uncaught errors
(04:52) Async example
(06:01) Path module
(07:17) How to write to a file with Node.js
(08:48) How to update a file with Node.js
(10:01) Nested operations
(11:31) Callback hell
(13:32) fsPromises
(16:02) Replace Callback hell with Async Await
(18:50) How to delete a file with Node.js
(20:09) Readstream for large files
(21.25) Writestream for large files
(22:15) Stream data listener
(23:19) Piping data streams
(24:04) How to create a directory with Node.js
(25:14) How to check if a file or directory exists
(27:03) How to remove a directory with Node.js
📚 References:
Node.js Official site: nodejs.org
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Was this tutorial about creating, reading, writing, updating and deleting files in Node.js helpful? If so, please share. Let me know your thoughts in the comments.
#node #js #files - วิทยาศาสตร์และเทคโนโลยี
In this Node.js tutorial, we'll explore the File System (fs) common core module. You will see examples of all CRUD (create, read, update and delete) operations for files in Node.js. You will also learn about the asynchronous nature of Node.js and how to avoid "callback hell" by using fsPromises. This tutorial is part of a Node.js for Beginners tutorial series. See the full playlist here: th-cam.com/play/PL0Zuz27SZ-6PFkIxaJ6Xx_X46avTM1aYw.html
It's refreshing to see a tutorial where someone mentions documentation they are using. Most of the times it's "let's put this absolutely cryptic line of code here because I said so".
Thank you - documentation is always an essential reference 💯
Super useful.
8 minutes in and you've answered every question I had right now.
(JS noob who installed node for the first time this morning as an alternative to doing everything in dev tools. Been wondering for a while if i could read/write files. Kind of crazy how thrilling it is to be sitting here looking at a list of 20 freshly minted random numbers in a simple ol' text file your tutorial taught me how to create.)
Many Thanks, once again, for sharing your knowledge.
Will be checking out your full node tutorial for sure.
Glad I could help, Sam! 💯
This course is so underrated, thanks for this Dave!
Thank you Dave
These tutorials are gold
You're welcome!
Fantastic vanilla Node tutorial. Concise and practical. Thank you, Dave!
You're welcome, Cameron! 💯
Any recommendations on serving images from a server? I realize the main options are to store the image in the file system, then use some string identifier in the database or elsewhere to fetch the image, or save the binary data in the database and read it when ready. What’s the best way to serve an image from a GET request?
@@tf1n often the API just responds with the image location - possibly in an AWS S3 bucket - and the HTML or other frontend tech pulls the image in from that remote resource.
The best channel ever! Thank you for the awesome tutorial! 💛
learning how to handle system files is very useful when dealing with things such as logging, caching, loading/importing external files into the app (maybe exported from Excel as csv) and many other scenarios ,
about the uncaught exception (or any similar event available in other languages), I tend to implement it at the final stage in my app development progress so I can immediately notice any exception may occurs (as I forgot to look at the console most of the time),
of course I'll be implementing it once my app functionalities are well tested so any error may occur could be due to unpredictable/Uncontrolled external causes (environment settings, server load/crash, file corruption, etc.. ), at this point it's good idea to log what happened there and maybe report it to the developer,
Thanks Dave for the great work and I hope to see you in the next video
I agree with all of the above my friend! Thanks for the comment 💯
I am loving this series 👍
nice tutorial! Thanks Dave
You're welcome!
I loved this tutorial... Thank you Dave!
You're welcome, Jenny! 💯
I applied this tutorial to read a JSon file and it worked well! Thank you Dave, you really made this task simple and easy to understand!
Glad it helped! 🚀
Hi , did you use this tutorial to work with bulk json files or just a single json?
@@archanaknayanar2500 Hi, I used a single json file
This content is by far the best. Thank you for this labor of love. It's going to change my life.
Thank you!
Awesome Explanation.. In an easy to understand manner
Thank you! 💯
Awesome video Dave! Your video helped me.
Glad to hear it!
Thank you!
Thank you Dave Gray you're the best
You're welcome!
Hey, thanks for this! i am really insterested about how things work in a full developed web application, this thing really helped me!
You saved my life!🎉
I love your content so much! Looking forward to new Nodejs tutorial videos. Love from Vietnam
Thank you! And hello 👋 to Vietnam!
Thanks for the explanation about why it's better to have the use appened file inside the write file function. I've seen it done before but didn't know why it might be useful. I didn't realize append file was capable of writing a new file also; so now it makes sense to have it operate 'after' write file.
You're welcome!
Just want to say, GREAT TUTORIAL!!!!, Thank you
You're very welcome!
it really helped me.😍
Glad to hear it! 💯
Really really nice!
Glad it helped!
thanks so much for this helpful tutorial
You're very welcome! 💯
Best of the best of the best. Thanks you
Loved the tutorial, it'd be nice if you could show us how to stream huge data from backend to frontend in a mern app.
Great Content
Thank you! 💯
Great video sir you have explained fs module very clearly and in a very good way. Thanks a lot sir. 🙏🔥😊✅❤️
You're welcome! 💯🚀
Amazing tutorial thank you
You're welcome, Sona! 💯
@@DaveGrayTeachesCode Thank you Dave
🚀
Yoy Save Mi Life with this video!!
Happy to help! 💯
You make really good tutorials. I have been using Nodejs and express for about six months and for the most part I understand how it works and I love using it. I know I will learn a lot from these series about native Nodejs.
For some reason I don't really get errors in Javascript or Nodejs or even express. There are exceptions, errors, handled errors, uncaught exceptions, error handlers and then you add try and catch to that mix and the whole thing is so confusing. Personally this is the most difficult concept to understand in Javascript. Is there a resource you could point me to that would help clear the confusion or maybe that's a tutorial idea for you. Kind regards
I agree. Errors are no fun and can be confusing. Handling errors in NodeJS could be a tutorial topic, but overall, I was good with showing how the docs say to catch uncaught errors and give an example of try / catch here. For Vanilla Javascript, I have a short tutorial on handling errors, too: th-cam.com/video/blBoIyNhGvY/w-d-xo.html Thanks for asking! 💯
@@DaveGrayTeachesCode Thank you for the prompt reply. I will watch the video from this link. I really appreciate. Hopefully I get around Nodejs errors before your tutorial but I am sure I would watch your take on it. Thanks a million
Very nice, thank you. At the end with an if-else would be enough? Thank you
Thank you - I need a timestamp to reference a specific point in the video :)
Thank you, Dave, it will be how many parts? I love your Node.js serie
You're welcome 🙏 I have at least 3 more tutorials before adding in the Express JS framework.
@@DaveGrayTeachesCode thank u , will u add mongodb part also? :)
@@kenansari yes, that will come after Express JS 🚀
Thinks
Kind Regards!!
🙌
Thanks for your useful content, i have quick question, how to read a docx file source and create a new file in local directory for download.
I haven't used it, but you might try this Github repo. It looks useful for your docx question and has specific examples in NodeJS: github.com/mwilliamson/mammoth.js
Amaizing video, pity that the source code is not available
What is your take on DENO! It started out earlier like a 'gang buster', hot. Now it has slowed down. Have you tried it? do you think it should be used?
Great question! I have not explored Deno. Like many, I waited to see if it would take hold... maybe too many of us waited and kept using Node. I've heard good things, but I currently do not have experience with it.
Oddly, I followed your code to the letter and the console.log() ends up writing to the console that the writing was complete before it read from the file and I can't ascertain what is different or why this happens.
Hello. Many thanx for such a wonderful video.
Could you explain, please, this data[, options]. Why is comma insight [ ] ? what does this mean ?
Anything within the square brackets is considered optional when invoking that function/method. In that instance it's saying if you don't use the options parameter, then the comma isn't needed either.
Well, this is a bit of a conundrum. At 27:58, the creation then deletion of the 'new' directory does not work in the same manner. If the 'new' directory doesn't exist, it creates it; if it does already exist, it deletes it. However, it doesn't do both at once, create and then delete it, as in your example. I've checked the code thoroughly and it's identical to yours, Dave. Any idea what might be going on here? It's as if it's evaluating the second if condition BEFORE the creation of the 'new' directory in the first if condition has completed.
That's a good and interesting question - this could be related to the async nature of Node. I possibly should have addressed it with this example as well as I did early with the files. Try nesting the deletion in the callback of the creation.
@@DaveGrayTeachesCode Yep, that's fixed it. It will be interesting to hear if anyone else experiences this problem.
@@andrewclarke6916others may easily experience the same. The async action of creating the directory may or may not complete before the attempt to delete the directory. Nesting in the callback orders the sequence. You could also use fsPromises with async / await as I displayed with file ops.
@@DaveGrayTeachesCode I'll give that a try too.
@@andrewclarke6916, same happened with me.
Great video Dave, can you advise how can i append content to a specific line? I want to read the content of HTML file (which works), then identify a specific line that contains then add user input value from a form, and append another 5 lines of specific content after the title line.
You describe a nice JS challenge assignment here. There is more than one way to accomplish this. I won't write the exact code for you, but reference MDN for methods like slice and indexOf. This stackoverflow post may be helpful, too: stackoverflow.com/questions/20817618/is-there-a-splice-method-for-strings
@@DaveGrayTeachesCode Thanks for your feedback, i have made it last night already, the script works as I described, mostly thanks to you and some luck that i found the right sources. Now i am working on getting FORMDATA from front end, past it to back end and run the script. If you have any video suggestion on form data sending to back end, especially that file input and text input needs to go in the same package, i appreciate every suggestions
@Balazs Kovacs this tutorial loads formData to the backend: th-cam.com/video/4pmkQjsKJ-U/w-d-xo.html
@@DaveGrayTeachesCode Thank you, i hope i have my result by the morning :)
Hi Dave Grey, i want to read JSON file and keep updating the multiple keys in a JSON file. Can you please help how to achieve that
Keep going in this series. You will see an example of working with a JSON file.
callback functions, error handling, async await
hey dave i have a issue with createreadstream it works perfectly iam using csv file for reading but 10 out of 1 time my readstream doesnot read my file i dont know why can u please with me with this it would be really greatful
I could only guess, but you can ask and provide more information in my Discord here: discord.gg/neKghyefqh Viewers help each other and I answer questions there, too.
How about if we have to store file in another directory which is not there under app directory. Thanks
If I remember correctly, this video also shows how to create new directories.
Thank you..
12:35 - Why when I'm running the exact same code, the read operation doesn't complete before the others?
In my case it is:
"Write complete - Hello my name is (Reading cimplete) - Rename complete - Append complete.
..?
You're welcome, Louis. I cannot be certain what may be different for you, but my only guess is that the fs.rename in your file is not nested inside the fs.appendFile ?
@@DaveGrayTeachesCode Your guess is most definitely make sense and unshockingly - correct. Thanks!
existsSync function is behaving different in my code. Even if you write same code, for the first time it only creates new directory and if you run it again it removes the directory. What's reason behind this strange behavior??
It should work as I have demonstrated. You can check the docs here: nodejs.org/dist/latest-v16.x/docs/api/fs.html#fsexistssyncpath
I don't understand: on 28:02 when console logs both "removed" and "created" - how it can be possible?
fs.existsSync is sync action so when we enter "IF BODY" we place async callback - mkdir to our async queue. So when we move to the next if statement - our directory does not exist. Am I wrong?
As you can see the code executed and explained - yes, you are wrong. Just watch at 27:40 where I run the code. It creates the directory and then it removes the directory. I don't think I can demonstrate or explain it better than I have in this video.
@@DaveGrayTeachesCode Thank you Dave. I'm sorry for asking the same question that other people had already asked. You already gave a good explanation in comments below - I just didn't notice.
@@denmccormik7654 no worries!
At 9:30, I didn't understand why readFile completed last. I thought read, write and append were all asynchronous?
And at 11:25 again, I also didn't understand why the result came out in that order. Please help me with this
I get it now... Thanks Still:)
What's the difference between writeFile and createWriteStream?
One uses a stream. I provide examples of both here and am not sure how to explain better than I do in the video. Docs references: writeFile: nodejs.org/dist/latest-v16.x/docs/api/fs.html#fswritefilefile-data-options-callback and writeStream: nodejs.org/dist/latest-v16.x/docs/api/fs.html#class-fswritestream
heyy, i have poblem filesystem.writefile does not create file
please help
I can only suggest to Google your problem. I cannot see your code and can only guess about why it doesn't work. You can rewatch my example that does work as well.
How to read from postman
Keep going. This series will get you there although I use ThunderClient instead of Postman. Same concept.
20:13
Is that also possible with a button
Yes. However, Node.js runs on the server and while you can build frontend files to be served, it is often just used for the backend (server) code.
thank you for your fast Answer, I would like to write the time with a button in a file. I use xammp, and i have the feeling that nodeJS dont works with my xammp and Apache Installation. I have created an js script with the node js instructions, and one php file with html button, i saw the constellation in a video. But in my case dont works that Method, and i dont know why. Would you make an video for that
TOO much Depth 😅