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Home / Video / 03. Web3.js Tutorial – Attach a GUI to your Ethereum Smart Contract

03. Web3.js Tutorial – Attach a GUI to your Ethereum Smart Contract



Free Course Web page (In growth):
Written tutorial of this video:

This video is the third lesson from my 100% free course:
“Creating Ethereum Smart Contracts for Rookies”

Test it out right here:

On this video, we’re going to take our good contract we created within the earlier lesson, and make it accessible through a net web page with the assistance of the official Ethereum Web3.js shopper and Ethereum-testrpc.

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49 comments

  1. I did the same except with nodejs as server, the coursetro object returns all successful, but for some reason, teh getter and setter are not getting called from front end script.. can you please check if possible?
    https://github.com/parthi2929/my-second-dapp

  2. wullah this sh%* is black magic praise coursetro our lord and saviour

  3. I get this syntax error when I run the testrpc command. Any idea why?

    node_modules/ethereumjs-testrpc/build/cli.node.js:71649
    function VM (opts = {}) {
    ^

    SyntaxError: Unexpected token =
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:387:25)
    at Object.Module._extensions..js (module.js:422:10)
    at Module.load (module.js:357:32)
    at Function.Module._load (module.js:314:12)
    at Function.Module.runMain (module.js:447:10)
    at startup (node.js:140:18)
    at node.js:1001:3
    ~>

  4. Hi, First thank you for your great effort.

    I got two errors:
    The following error when i refreshed the page:
    BigNumber Error: new BigNumber() not a base 16 number

    And the following error when i clicked on "setInstructor" button:
    Error: The MetaMask Web3 object does not support synchronous methods like eth_sendTransaction without a callback parameter.

    Why did the errors occur??

  5. i am getting the error at npm install ethereum/web3.js –save. Please help me

  6. If you get an error connecting to testrpc server, you just need to change remix to use http protocol instead of https.

  7. I wrote similar code, but when try to call setInstructor, getting error Uncaught Error: invalid address

  8. hello, firts thanks the course. I have this error: new BigNumber() not a base 16 number

  9. when i try to setInstructor i get this. Uncaught Error: The MetaMask Web3 object does not support synchronous methods like eth_sendTransaction without a callback parameter.

  10. Uncaught Error: VM Exception while processing transaction: out of gas

  11. what install of visual studio? can i code on phpstorm?

  12. this is a great tutorial!

  13. why we need a default account in index html as that contract was already created by another account in Remix?

  14. hello can you help me i follow all the steps but the result not show on Remix

  15. Just Write your <div> code inside the <form method="post"> you will not need to refresh the page for result..

  16. why do we need to pass address at CoursetroContract.at(address);

  17. Ops, ERROR at npm install ethereum/web3.js –save
    npm ERR! code ENOGIT
    npm ERR! No git binary found in $PATH
    npm ERR!
    npm ERR! Failed using git.
    npm ERR! Please check if you have git installed and in your PATH.

  18. Thanks for the explanation ​but i have few questions on this.

    I have a plain HTML page hosted on Azure Web Apps and a Blockchain running in a VM which exposes its end points
    1) should i mention its end points in "httpproviders" ?
    2) if i change the contract ,should i come and change ABI and contract address manually or is there any better way of doing this?
    3) if i have to access any dApps hosted online, do i need to have Metamask installed in my browser for sure?
    I would be very happy if you provide me a detailed explanation on this.

  19. when i click button , error : Uncaught Error: invalid address … . help

  20. Hey.. I'm unable to successfully install ethereumjs-testrpc as when I type testrpc it says that it doesn't recognize the command internally or externally! what do i do?

  21. Web3 Account not working properly.

  22. while installing web3.js i am getting rollbackFailedOptional: verb npm-session f80a1fa0cd539721
    can anyone please help

  23. error – BigNumber Error: new BigNumber() not a base 16 number

  24. FYI, my version did not work until I changed this line in index.html from:
    “`
    <script src="./node_modules/web3/dist/web3.min.js"></script>
    “`
    to this:

    “'<script src="./web3/dist/web3.min.js"></script>
    “`

  25. I am getting error. any one short it out.

    C:ethcoursetro-eth>npm install ethereum/web3.js –save
    npm ERR! code ENOGIT
    npm ERR! No git binary found in $PATH
    npm ERR!
    npm ERR! Failed using git.
    npm ERR! Please check if you have git installed and in your PATH.

    npm ERR! A complete log of this run can be found in:
    npm ERR! C:UsersPavan-VeebrijAppDataRoamingnpm-cache_logs2018-03-21T14_13_52_175Z-debug.log

  26. HELP!!! i did same as u suggested in video but I am getting error when i run HTML File in Google Crome
    uncaught ReferenceError: Invalid left-hand side in assignment
    :web3=new Web3(new Web3.providers.HttpProvider=("http://localhost:8545&quot;));

  27. Gary, Thanks for the videos. While executing this step npm install ethereum/web.js –save I am getting GitHub console. I do have an account in GitHub, but getting an error Host key verification failed. Why it even has to interact with GitHub?
    npm ERR! fatal: Could not read from remote repository.
    npm ERR!
    npm ERR! Please make sure you have the correct access rights
    npm ERR! and the repository exists.
    npm ERR!
    npm ERR! exited with error code: 128

  28. Uncaught TypeError: t.abi.filter is not a function
    at u (web3.min.js:1)
    at p.at (web3.min.js:1)
    at index.html:47

  29. Спасибо за отличное видео, коротко и понятно!

  30. Hello ! can you show me how to call the constructor with arguments from web3

  31. how could we contract cmder with vscode ???? this file of code in vscode from where ? …. i was install vscode after doing this steps ,,, and i return it again after insall it in cmder !

  32. testrpc has been renamed to genache-cli but gebache-cli is nolobger supported

  33. Great video please go ahead making stuff so helpfull like this,
    I got a Question everything is working working but when I open the console to see and deploy "all events does not show me one"
    if I want to set a value with setInstructor('Brutis', 44) does not work because does not find the method

    thanks a lot .

  34. Cmder does not work, but regular windows CMD does. Too bad, I like the Cmder UI better.

  35. Thanks for share this great course

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  37. C:Usersadmincoursetro-eth>npm install etherum/web3.js –save

    npm ERR! Error while executing:

    npm ERR! C:Program FilesGitcmdgit.EXE ls-remote -h -t ssh://git@github.com/etherum/web3.js.git

    npm ERR!

    npm ERR! Host key verification failed.

    npm ERR! fatal: Could not read from remote repository.

    npm ERR!

    npm ERR! Please make sure you have the correct access rights

    npm ERR! and the repository exists.

    npm ERR!

    npm ERR! exited with error code: 128

    npm ERR! A complete log of this run can be found in:

    npm ERR! C:UsersadminAppDataRoamingnpm-cache_logs2018-05-31T09_39_14_406Z-debug.log

  38. console.log(Coursetro); returns 5.278065910509934e+47 instead of 0x5c73aa85449d9efca09e430f6947a0a9372425b0
    though I can see getInstructor and setInstructor in console
    but contract.getInstructor(function(error, result){ }); returns with web3.min.js:1 Uncaught Error: invalid address

    Can anyone help?

  39. Getting "Web3 is not defined" error.I have tried all possible providers for it.What are the other things should we be doing simultaneously which causes error in its abscence. Please help me fix it.

  40. These tutorials are DEPRECATED!

  41. When I click button I get error:
    inpage.js:1 Uncaught Error: invalid address
    at c (inpage.js:1)
    at inputTransactionFormatter (inpage.js:1)
    at inpage.js:1
    at Array.map (<anonymous>)
    at i.formatInput (inpage.js:1)
    at i.toPayload (inpage.js:1)
    at n.e [as sendTransaction] (inpage.js:1)
    at u.sendTransaction (inpage.js:1)
    at u.execute (inpage.js:1)
    at HTMLButtonElement.<anonymous> (index.html?_ijt=nqe55ga5kc1m9el5qvjohvtkeo:95)

    I did the same as in video but I get error