Creating a blockchain with Javascript (Blockchain, part 1)

[@tauwheed3055]

I do not understand anything about coding, but the way this mysterious gentleman stated everything, I was completely hooked up seconds by seconds till the end. I guess some peoples do have some extraordinary quality of teaching. Thanks Savjee

[@ViralVeediuh]

Tauw heed it’s that you actually care about learning about blockchain. Trying watching a video on programming a microwave keypad. Much less interesting lol

[@BigDaddyDax]

Agreed!!

[@BigDaddyDax]

@@ViralVeediuh true

[@aayushpratapsingh5860]

Same here

[@pajamasoverpeople4412]

SAME.

[@FacundoTroitero]

After +1 year of courses, projects documentation and tutorials I could finally understand how Javascript classes work thanks to this video. Thanks!

[@VivaLaaLIBERTA]

Keep Walking, now you start Easily understand everything else.. Everything will Open to you.. ;))

[@vegn_brit5176]

Great video. I'm a programmer so this made a lot more sense to me than watching someone try to describe how the blockchain works in a spoken presentation!

[@owenparker6651]

Savjee, I have finally been compelled to subscribe to a youtube channel. As an 'old dog' programmer, you have got me moving on blockchains more than the dozens and dozens and dozens of articles I have read. For a 'show me' programmer, this is just what the doctor ordered and I thank you for taking to the time to share your knowledge and for doing such an easily understood walk-through. Well done young man...

[@simplyexplained]

Thanks a lot! Reading your comments made my day!

[@blackswan7568]

For my internship, I was recently requested to do a simple web3-based project. This is what I've decided to use. Thanks for this project and for being a great teacher😁

[@mauriziomaisto2874]

Great tutorial, thank you. I was "playing" with your code and i've just discovered that changing the "Genesis block" (block 0) attributes is possible (the chain stays valid). This is due to the "isChainValid()" method; as you can see, the method has a "for(var i = 1; i < this.chain.length; i++){ [...]" which starts from "i = 1". This means that no controls are applied to the first block (data can be changed without any problem). A simple work-around is to change the "for([..])" loop (make it starts from "i=0" and check the previous block only "if(i>0)"). Thanks for your time and knowledge

[@saxenaabhi]

Oh man, after watching heaps of videos on bitcoin, etherium and block chain. This is the first time I really got my head around only because we think in terms of code. Love you for that.

[@joeysipos]

yeah, seriously. All these explanation videos make no sense. But looking at how the code actually works make perfect sense haha.

[@astrarai-thesobercoder]

Same here 👨🏽‍💻

[@jasonpatel6562]

@@joeysipos if(currentBlock.hash !== currentBlock.calculateHash()){} TypeError: currentBlock.calculateHash is not a function : thats the error I got, not sure why it is function

[@Procyon58]

So much information fit in this 15 minutes and this finally made blockchain click in my head. Thank you for this!

[@niklavr]

Yes! Really helpful video! Thanks!

[@luckyadeloye3452]

Especially the explanation of difficulty and nonce.

[@seanrosen9855]

Exactly! Over all those explanations online which doesn't provide any example, I can finally understand the base concept of a blackchain after watching this video, thank you soooo much. Autosubs

[@nitinchaudhary7686]

How can i make zsh in terminal

[@stanicng]

Same here. I think we belong to developer world. Simple words can't make us understand until read the programing logic. Hehe.

[@lucysluckyday]

My gosh, in terms of covering the basic fundamentals this is an amazing intro!

[@shorttripsvn1444]

Major in Law but I think this guy has successfully guided me through the jungle of IT and let me know a little bit of how Blockchain are created and its security mechanism

[@TheStoriesProductions]

"Simply Explained" indeed ! Amazing, cleared a lot of concepts.

[@CourtneyZinckgraf]

I know nothing about coding, but this example really made me understand what's happening with blockchains - thank you!

[@prabhusingh7481]

Demystified this for me, finally! Thank you so much for making these concepts so tangible.

[@fernandofradegrada]

Very clean explanation, and also very clean english for those who doesn't speak english natively. Thanks!

[@simplyexplained]

I'm not a native speaker myself, so I have to keep things simple ;)

[@vasanthkumar2190]

This looks similar to linked lists in Data Structure with added security!

[@cazino4]

Great observation!! It is similar to a Singular Linked List data structure With one massively important improvement namely: O(1) (i.e constant time access) to all blocks in the chain, via the top-level array.

[@Mailmartinviljoen]

May i nitpick? The focus is on integrity which make it inherintly secure 😁

[@frumpledpigskin]

i was thinking the same thing

[@SatyamGupta-gc9sq]

@@cazino4 yup it's linked list but not singly linked list, it's doubly linked list as it stores the adress of the previous block too.

[@cazino4]

@@SatyamGupta-gc9sq Nope, you're INCORRECT!! Please revisit the source code - it is quite clear. The presented Block Chain data structure has more commonalities with a SINGULARLY Linked List, NOT a doubly linked list as you have attempted to suggest. Whilst I agree that the structure does indeed store reference to the previous node (i.e its parent) it DOES NOT *DIRECTLY* store reference to the NEXT node. Thus it's essentially a singularly linked list in reverse.... But STILL a singularly linked list nonetheless. Source: myself lol. I've actually built these types of core data structures (i.e Singularly/Doubly linked lists, Binary Search Trees, Balanced Binary Search Trees,Tries,etc) from scratch in numerous languages and have a deep understanding of matters pertaining to their. respective implementations,trade-offs, time-space complexity,etc

[@breal1460]

Thank you for sharing this. Today I decided to learn about blockchain. I hope I can learn enough to produce something to help make our world a better place.

[@jessss7792]

Very well done video. Steady pace, clear code, and an engaging voice. The blockchain just became a whole lot less intimidating and mysterious, so thank you.

[@MadhavanR]

Noticed this video on my recommendation and in 15mins understood the basics of blockchain… most importantly the simple and powerful sample you showed👍🏻👍🏻👍🏻

[@Ricardoromero4444]

Damn bro, that light theme doesn't hurt your eyes?

[@snikkerrr286]

😂😂😂😂

[@hansphung]

and the bracket on the same line with the parentheses and no space, ew

[@slavento]

Try working in very light room...it's common to work with light theme in that case, and with dark theme in darker rooms...

[@rangarajann1781]

@@slavento yeah using dark theme in bright light environment is not good. Dark theme is perfect for only dark environments. And light theme is good for brighter environments

[@jorgepvenegas]

Does anybody know which theme is he using?

[@mstafadev6729]

I've watched too many videos to understand what a blockchain is and none of them seemed to help, but this video clears things up in my head about blockchain, Thanks

[@clementbourcart785]

Love this! Thanks so much for making this tutorial, really helps a non-techie like me get under the hood of blockchain!

[@josephcobbinah5412]

The first video about Blockchain that I actually understood

[@classborn]

Subbed , you brought tears to my eyes.

[@kukuster]

exactly. That's why dark theme *is better*

[@FreedomForKashmir]

I swear, this is the video finally where I really understood the concept of Blockchain. I have watched many videos but was getting just repetitive things time and time again. Thank You very much. I have like and subscribed to you channel.

[@mi13estrellas]

would implementing some of those other features such as "proof of work/ stake", check of funds, ability to prevent tampering of data / rollback function be possible to demonstrate in another video? It would be greatly appreciated.

[@daezohn8662]

Not to mention P2P network consensus and transaction broadcasting. I sometimes think writing your own blockchain is just as ambitions as writing your own OS. Maybe it is just easier to take to bitcoin code and adapt it to your needs.

[@utopialabsvideos9408]

@Sophie, do you want a complete implementation? Just read the source code for Bitcoin or Ethereum...

[@lucysluckyday]

Yeah the actual source code is the best option when you want to understand the more complicated aspects of merkle trees, nonces, unconfirmed transactions, and memory pools. But this is an extremely good generic intro on the fundamentals !!!

[@jagodiving]

there were a few genious on algorithm n coding, but i think you one the best amid them....simple n clear

[@JavaScriptRoom]

Hey! Thanks for the great content! One question: why didn't you generate block's index and timestamp on a fly in the constructor? Is there any reason for passing them on instance initiation?

[@oderingpush8054]

hello, has this improved your knowledge of java and blockchain? have you made any progress on creating a blockchain? i would like to talk with somebody who might be able to help me script a source of a new blockchain

[@nestoreduardoirahetamazari9409]

Great! I was learning blockchain but with a traditional school teaching for weeks and I didn’t understand nothing but with your videos I completely hooked up great and very simple way to learn thanks and appreciate to share your knowledge ❤

[@jekabolt]

it's will be great if you create a. video about smart contracts

[@simplyexplained]

That's a nice idea! I'll definitely consider that!

[@python_tutorials6519]

yeah pls do that and can u include dates in smart contracts for tokens to be distributed only during that time?

[@simplyexplained]

+Python_Tutorials Great idea! I'll think about how to implement that :)

[@python_tutorials6519]

great,thanks a lot and we would love to wait for that video

[@arhabersham]

WORD!

[@supratimbasu1461]

These hands-on turorials really come in handy to grasp the blockchain concepts. There's this scenario where tampering the data of the final block in the chain will lead to the block getting invalidated due the mismatch of the hash generated post-tampering with the existing hash of the final block. So, this will prompt a "false" in the chain validation. But, if we recalculate the hash after tampering with the data (only for the final block), it prompts us the chain being valid since the hash has been regenerated (modified after the hash mismatch). Thus the validity of the chain turns out to be "true" which is sort of a glitch from the blockchain conceptual perspective, but is correct from the logical point of view

[@SwadeshiBakchod]

13:02 Blockchain is like "Mr.Stark...I dont feel so good..."

[@laude94wuo]

Clear coding style makes a complex concept to be so easy that everyone can understand! Amazing...!

[@AmitYadav786]

Awesome intro, I think you should make this a series so that people can make their own full blockchain using your details. When is the next video coming??

[@simplyexplained]

+Amit Yadav Great idea! Next stop would be to discover smart contracts. Definitely will work on that in the future. But first I need to finish another course ;)

[@simplyexplained]

+Amit Yadav Great idea! Next stop would be to discover smart contracts. Definitely will work on that in the future. But first I need to finish another course ;)

[@nitinchaudhary7686]

Amit Yadav how can i make zsh in terminal?

[@stanfordnwosu424]

Simply Explained - Savjee Heyy any luck with making those blockchain courses

[@md.jayeenbinalam.6194]

The best beginner level blockchain tutorial.

[@augre-app]

great video. subscribed!

You could use for(var i in smth) instead of for(var i=1;i

[@simplyexplained]

Yep that's right but then I would need to keep a reference to the previous block.

[@hashmoody]

Really great, that sparked a great idea in my mind! :) (y)

[@amnest1ac]

This is so easy. For all the noise this "technology" has made. I am impressed how fundamentally basic is the idea itself.

[@mattyzacharia]

Great video. Congratulations. I have a question though, in the example, I tried to tamper data and did recalculation of current hash and assigned to existing hash. I got output as true. We are not tampering anything with previous block hash. Basically I have not understand the check on current block hash with the previous block hash as for me it always return true. Also if I carefully watch video , when you do a tampering and set current hash. It gives output as false. However if I examine your console which is on this video, both previous hash and current hash seems to be identical. Then how does it return false? Thanks Matty

[@dukewellington5222]

Did you put the return true statement in the body of the for loop?

[@mzaki8503]

I am having the same exact problem now. Did you manage to solve it?

[@Chris-oe4pj]

when isChainValid loops and checks the block that is right after the one you changed, its previous hash will not match that preceding block's new hash that you had calculated

[@Mailmartinviljoen]

Clarity by far the best tutorial i have ever seen

[@albertkeller3773]

How can I download the library on Windows? Because on windows the terminal is working with powershell

[@AbdulAhad-ni4hq]

same problem here did u solved ?

[@safaelboukhari5431]

@@AbdulAhad-ni4hq same probleme :(

[@alvarovalenzuela7389]

use bash instead :)

[@eoussama]

You need npm installed.

[@robincard1548]

If you're really serious, I would switch your desktop from Windows to Ubuntu Desktop (free) or run Ubuntu in VirtualBox (free). Windows and Node/Javascript don't play well yet, there are still lots of problems with file names and stuff. The windows guys I work with are always having problems, the people on the *Nix/Mac system dont have these problems ever. I'm not saying Linux/Mac is better than Windows, just saying that for now JavaScript is better on Linux/Mac. They my fix it soon.

[@talkbackmovies]

This is so strange. I have watched tons of videos on blockchain and as a programmer it took watching this video in code language for this to be fully understood. Hilarious that english seemed more obtuse than pure javascript code to explain this concept. I even can now extrapolate how to write a code for correcting a chain after a change (iterating with a method that will match various tags ie timestamps etc) and also even how a proof of work might function. Great video I think aimed directly at coders.

[@calvinlin6670]

It's a great explanation video of Blockchain. Can you tell what IDE you are using 0.0 Cuz i really like the UI , thanks

[@RoadToFuture007]

Hafrn The Grey white edition ;)

[@MistaT44]

Press ctrl k + ctrl t, and select the quiet light theme :)

[@zhangbruce4815]

Best block chain explanation video so far I've seen

[@tharhtoo2149]

Thank you so much, Sir. You just make the whole concept of blockchain sys clear for me in just under 15 mins.

[@sreelalts1892]

Amazingly explained! I really didn't know anything about Blockchain. After watching this video, I was like "wow, this guy is amazing!". You did it so nice Savjee! Thanks a lot!

[@Chrosam]

Great tutorial to start with Just to add, you can recalculate all hashes after you tamper with a block which should return that the chain is valid

[@dukewellington5222]

Explaining it in code makes blockchain technology so much easier to understand. Thank you for this! Great job!

[@DevilOrange666]

Finally understood how magic internet money works. Awesome video!

[@SM-yf1tp]

Not going to lie, I’m brand new to this and I have no idea what just happened here. But I liked it!

[@ulfkarlsson272]

Thanks, I had the theoretical understanding of what a blockchain was before, but seeing it explained this way makes everything much clearer.

[@nellynelson965]

Ive no idea how to code, but I mine and I wanted to understand a bit better. Thanks. For me it was the simplest example I watched and now understand it a bit better.

[@itshiraljain]

You simply explained and I simply subscribed. This is what I was searching for as I don't knew any implementation of blockchain. thankyou

[@mizlagunesvary5077]

Wow.. Thanks, Sanjeev for this video. I`ve been searching for something to enlighten my brain with what`s actually Blockchain is. Finally, you did it... Thanks man

[@ib6435]

Watching this in 2020 and its broadens my programming knowledge. Thanks!

[@mubafaw]

Wow! This explanation demystified the whole concept of blockchain . Thanks 😊👍

[@lovebajpai5288]

Fantastic!!! What an explanation! it just makes you understand the whole thing in one video!

[@osraneslipy]

Thank you very much, I think this is absolutely the best way how to explain how blockchain works (assuming one knows javascript or other similar language).

[@jacob_dmn]

so so helpful, I can't believe all that happened in 15min. Love it. Please keep it up

[@Frank2tek]

Best and simple way to understand the core concept of blockchain . Nice job ...

[@joyhearrington8503]

You are a great teacher, Mr. X! Thankfully, I do not have to write this code but I needed to understand blockchain for my graduate class. This video finally made it all click! (I watched your other one before this too and that was helpful as well.) Keep up the great work and thank you for sharing it for free!

[@AhmedEssam-lv5vn]

New info that I have read: DO THAT: for (let i = 1; i < this.chain.length; i++) { // CODE } INSTEAD DO THAT: let chainLength = this.chain.length; for (let i = 1; i < chainLength; i++) { // CODE } The first method will always recalculate the array size in everytime it loops, but in the second method it will calculate the array size once. I just knew this info and I would like to share it with you guys because it will be helpful in large projects .

[@097_shashanksahu6]

Sorry thats not the case.. chain.length runs in O(1) time.. chain.length is a variable not a function.

[@adriancelis9691]

This is amazing. I dont even do Javascript (just php) and i understand what you're saying. Great vid.

[@pawelkozlowski6411]

i watched the whole thing ,didnt understand anything but it was fascinating ure a genius

[@leezhenjian7451]

Very intuitive way to explain about blockchain. Thumbs up!

[@AhmadNasikun]

Thanks for the great tutorial. There are lots of videos describing how blockchain works, but only a few that give some technical example(s). Among those few, this video stands out really well. For those who are new to blockchain (e.g. me), this video is really enlightening.

[@WhatIsThisAllAbout]

thanks man...I was wondering how this works in code & thats what you explained so clearly.

[@chunkin9799]

Clutch video. Excellent explanation of block chain. So much simpler of a concept than when you just hear it explained.

[@shivaskanthan6144]

Excellent 11/10. Detailed, concise and easy to understand.

[@sabhab1]

Your explanation demonstrate why Blockchain and its child cryptocurrency is unstoppable & secured. Many Thanks for the code ....

[@bobsmithy3103]

Wow, amazing job man. I've only covered the basics of Javascript yet your explanation of every part of your code made everything so clear. Your name really does suit the quality of your content. Thanks a ton man!

[@simplyexplained]

Thanks for the kind words! Makes my day ;)

[@tactteam00]

You gave an efficient and easy to understand intro to blockchain development. Subscribed

[@simplyexplained]

Glad you liked it!

[@AkhilPrabhakaran]

Wonder I didn't come across your page months ago. Not just for this particular video but the quality and the clarity in all your videos are amazing. Huge fan!!

[@KusaasiraNoah7421]

So much info in just under 15minutes. Thanks

[@chrissis111]

This was such a great video. I was amazed that you didn't make one error in your coding as you were going along, and you were "explaining" the whole time which was like watching some kind of super-human! Unbelievable coder!

[@simplyexplained]

Hehe, thank you! But I won't lie, this was well prepared in advance, so that makes it easier ;) I can't think, code and explain like this on a daily basis.

[@chrissis111]

@@simplyexplained Either way, pretty impressive.

[@mehdivand2977]

he explained in a simple matter , thank you

[@lakshmiprabha8271]

simply explained a complex code. Love this video

[@salararmakan6023]

First time Im seeing Javascript and coding and just learning about blockchain - I understood it. Lets mint this video :) ah and this is my first youtube comment ever

[@yashkolte7799]

So it's much like traditional link list, with added hash to prevent tampering. Thanks for the tutorial👍

[@AAli-lt9mt]

Really great video , wish i had this guy teaching me programming and coding as well

[@braianoso4138]

Love the way you explain things for a noob like me

[@ipungdevacademy]

Wow very simple explained ! thanks sir you are save my life!

[@NerdyKatsChannel]

I 100% agree with all of the positive comments. This was explained so cleanly and clearly, in perfect sequence. Thank you so much for making learning the fundamentals of blockchain so simple :)

[@simplyexplained]

Glad you enjoyed it! I would say: spread the word 😉

[@NerdyKatsChannel]

Simply Explained - Savjee Will do 👍🏽😁

[@gazisalahuddin8907]

Great, you understand concepts through building them. Thanks, man.

[@germandiagogomez]

Very nice introduction. Perfectly explained concepts in a compressed timespan.

[@SubhrajitSadhukhan]

Thanks man. This really helps understand the concept without going into too much or too little details. Exactly what I was looking for.

[@ugurceng32]

so simplified, thanks for "blockchain in a nutshell"

[@Иван-у4с9н]

All is really very simple and i understood the majority of things you said with my bad english(i'm russian). Thank you

[@gurzimm3213]

I don't even know how to code but this video made so much sense, great job!

[@flatearthcrypto6991]

this guy the only guy on utube as a teacher whi hasnt made me sleep. or fumble or waste time. just bammmmm. u know its right and good but soooooo many questions. lol. k im donee

[@luizdrumonddeandrade7065]

Just amazing how you have explained this topic in a really easy way. Congratulations!!!

[@Renizyne]

brilliant video, once i saw the code, i learned much more than they teach you in any other videos trying to explain blockchain using stupid powerpoint presentations

[@richaagrawal4416]

for the first time in life i have watched the whole info stuffed youtube video in one go. keep it up man!!

[@pynsukmawlong4928]

From this precious example one must first get the concept of data structures and algorithms to understand block chain efficiently.

[@minhmark.01]

Thanks for your video

[@gogoikabir]

amazing, now I understand something about blockChain

[@Shortly8908]

Thanks bro. I imagine blockchain works like magic until i watched your video.

[@torbilan6292]

Thanks , such a clean code and clear speech. Benefited a lot !

[@VincentNoben]

This explanation is so solid! Like others said in the comments, this is what made me get it. I sortoff knew but this made the click and will make it much easier for me to explain it myself in the future. Thanks!

[@broonzy2006]

wow! great video... I'm a low level dev and by watching the last 2 videos, really got the concept and quick application. Cool!