Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [web3js]

Javascript API and library for Ethereum To develop applications on Ethereum, you can use the web3 object provided by the web3.js library. Under the hood it communicates to a local node through RPC calls. web3.js works with any Ethereum node, which exposes an RPC layer. https://github.com/ethereum/wiki/wiki/JavaScript-API

0
votes
0answers
7 views

Setting array.length to 0 triggers an error on solidity 0.5.0

Why setting array.length to 0 triggers an error ? I have a function that deletes an element from a dynamic array of structs within a mapping as follows: mapping(address => MyStruct[]) public ...
0
votes
0answers
11 views

How to read uint256[] array from a method in a smart contract?

I'm using this function in my smart contract. It returns an uint256[] array containing the tokens that the user owns. /** * @dev Returns all of the tokens that the user owns * @return An array ...
1
vote
1answer
9 views

No web3 instance injected following the dApp University Tutorials

I've been following Dapp University's videos on how to make IPFS uploads with Euthereum Smart contracts, and after I manage to 'npm run start' in the command line it opens up the HTML, but it always ...
0
votes
1answer
14 views

Web3 - Cannot read property 'clearSubscriptions' of undefined

While creating a web3 instance, and attempting to call setProvider with a valid provider (Ganache), I get a TypeError. TypeError: Cannot read property 'clearSubscriptions' of undefined Steps to ...
1
vote
1answer
11 views

Auction contract problem regarding highest bid display

I have an Auction contract which has a function like this: function bid() payable{ //calculate and store highest bid value } But because each transaction takes time to mine, so when a user bids ...
1
vote
0answers
12 views

truffle unbox react - front end is unable to read / set state of the contract

I am experiencing problems with the Truffle React boilerplate code that the front end is unable to read / set state of the contract. Here are the details: I unboxed the React boilerplate using ...
0
votes
1answer
14 views

How do I deposit Ether to Smart Contract using Web3.js

So I am creating a web application that interacts with a smart contract that I deployed on the Ropsten TestNet. I am able to withdraw ether from the contract to my Metamask account using a withdraw ...
0
votes
1answer
39 views

Unable to deploy the smart contract using solc compiler in mac

I am trying to deploy the Lottery contract using solc compiler of verison 0.4.17 but it's showing me nothing. But the same contract is working good in the remix ide. I providing you the the Solidiy ...
0
votes
1answer
23 views

The method eth_sendTransaction does not exist/is not available on infura

Im trying to send transaction to simple greeter contract with web3.js on infura node.while doing soo, Im getting this error. throw errors.InvalidResponse(result); ^ Error: The method ...
2
votes
2answers
23 views

Metamask injects one account in web3, but calls contracts using another account

Building a React app, MetaMask injects web3, I get accounts[0] from getAccounts(), then pass it to my contract functions together with other parameters. I want my modifiers to lock incoming function ...
0
votes
1answer
19 views

signing transactions with web3.js

Im trying to create a node.js based dapp that interacts with ropsten ethereum network via infura node.here we need sign transaction with web3.js. but the code showing error from the contract side. ...
0
votes
0answers
23 views

Is latest block returned by eth.getBlockNumber fully processed

According to web3 docs, web3.eth.getBlockNumber returns the number of the most recent block. My question is simple. Is it safe to assume block's transactions and events are already in the node or ...
0
votes
1answer
41 views

Sending transaction with web3.js

I'm trying to use web3.js with infura.io to interact with my smartcontract. here is my simple greeter contract code pragma solidity ^0.5.7; contract greeter{ string greeting; function greet(...
0
votes
0answers
14 views

Contract has no network id set, cannot lookup artifact data

I am using web3 v1.0.0-beta.37 and truffle contract for server.js configuration. I have defined two contracts FlightSuretyData.sol and FlightSuretyApp.sol FlightSuretyApp contract access functions ...
1
vote
1answer
21 views

How to open metamask erc20 transfer window using web3 apis?

In my frontend I have 'withdraw' and 'deposit' buttons. I want to display the metamask screen that comes after clicking on the deposit and send buttons (of metamask) when the user clicks on the ...
0
votes
1answer
12 views

How to compare an address with an address using web3js?

I've been reading and trying but to no avail. I'm trying to compare the current wallet address in MetaMask with the wallet address which owns a certain token via a smart contract method "ownerOf" ...
2
votes
2answers
303 views

How to connect with public Ethereum Blockchain on a backend/web server?

In the backend of a Web application I have to communicate with the public Ethereum Blockchain. On local development machine, I run ganache as testrpc and connect with such a line of code: web3 = new ...
0
votes
1answer
20 views

Stop listening to / watching a contract (Web3)

Here is what I am trying to do (Web3 1.0): Deploy a contract Wait until Nth confirmation. Then stop getting updates from the contract. My code: var myContract = new web3.eth.Contract(_abi, ...
0
votes
0answers
18 views

How can I store the hash of a set of data in the ethereum and make the chain validated always?

I am working on a University Management System and I want to develop the system using Centralized Database like Mysql and to keep the data safe I want to use blockchain to store the hash of the data ...
0
votes
2answers
24 views

Load accounts to truffle

I'm using truffle v5.0.14 to handle my contracts. All was well while developing with ganache, but when I wanted to deploy to the real network (a private one) I have problems with the account. The ...
0
votes
0answers
16 views

how to send a payment transaction using web3js… and fetch contract address dynamically using web3js without hardcoding in app.js

function sendPayment(uint orderNumber) public payable{ //restricting only buyer of partitcular order can make payments require(Orders[orderNumber].buyerAddress==msg.sender); //checking ...
0
votes
2answers
41 views

How to wait for balanceOf before I execute a transfer?

Ok, I'm new into JS and web3 and MetaMask. I'm still lost about Promise and async/await after reading them for 5 times! I want to call my smart contract balanceOf method to check if there's enough ...
0
votes
0answers
19 views

Store data on ethereum blockchain from a text file

I have a simple smart contract running over a local Ethereum node. It has two functions: one for sending data and another for retrieving it back. I have a text file and want to send data from it to ...
0
votes
1answer
31 views

Unhandled promise rejection (rejection id: 1): Error: Transaction has been reverted by the EVM:

I don't know where i'm doing mistake. I have deployed my contract through remix and truffle and it was deployed without any mistake but now i'm deploying it from web3 solc@0.4.24 version and EVM is ...
0
votes
0answers
13 views

how can I transfer ERC20 tokens from user address to other user address using web3.js and ethereumjs,

This is code I have used to send tokens to other account from token holder account. below code is working, transferring token from contract address. Tokens: 500000 A Account having : 1000 Tokens B ...
0
votes
2answers
17 views

Why web3.version.api shows undefined for web3 1.0 and not undefined for web3 0.20.3?

I'm trying to use MetaMask and web3js to talk to my smart contract. Below are my test codes. This is without defining a web3 js file and I get the result "0.20.3" at console. <script> window....
1
vote
1answer
20 views

What is the difference between eth.contract and eth.Contract?

I don't get it. I've seeing two ways from tutorials on how to instantiate web3. One is.. eth = new Eth(web3.currentProvider) token = eth.contract(abi).at(contract_address); and another is.. web3 = ...
0
votes
1answer
44 views

problem of call() returns null

contract permission{ struct transaction { address payable sender; address receiver; string datatype; Status status; } function getTransactionCount() public view ...
1
vote
0answers
20 views

ERC20 Token support for metamask website payment

I have the following code working in my site to accept ethereum payments in my website via metamask.... <!DOCTYPE html> <html> <head> <script src="https://cdnjs.cloudflare.com/...
0
votes
1answer
38 views

Transaction stuck in 'Pending' state when using 'sendSignedTransaction'

I am trying to execute a transaction by first signing it with my private key using ethereumjs-tx and then using sendSignedTransaction to send the transaction to the network. But somehow the ...
1
vote
1answer
30 views

Not accessing metamask address through web3.eth.getCoinbase

I'm trying to run following code: App = { web3Provider: null, contracts: {}, account: '0x0', init: function() { return App.initWeb3(); }, initWeb3: function() { // TODO: ...
0
votes
1answer
19 views

Async getAccounts doesn't see my account

first time using MetaMask web3 Async getAccounts does not return my Eth account which I see in MetaMask. My fiddle https://jsfiddle.net/ysz11/qcv78h9z/1/ <!DOCTYPE html> <html> <...
0
votes
2answers
28 views

metamask and web3: Invalid number of arguments to Solidity function

my function has only one input string description : function createProposal(string description) { Proposal memory p; p.description = description; proposals.push(p); } and ...
1
vote
1answer
25 views

Reading events of the inner Solidity contract with Web3

Let's say I've got contract A { event E(); function a() public { emit E(); } } contract B { A private a; function b() public { a(); } } Now my Dapp is ...
0
votes
1answer
23 views

How to connect Trust Wallet in Javascript?

I want to use TrustWallet for payments in my project for mobile users. I saw the documents related to TrustWallet web3 API but not getting how to use it in javascript. Can anybody help me with the ...
0
votes
1answer
29 views

How to send struct data as function input on Remix or web3 call?

I've created a function which gets a struct which contains int+struct. Now when I want to test it, what data should I send for example on Remix: here's the code, got from another SO question on - ...
1
vote
1answer
24 views

Can the Android Metamask Extension be used with DApps?

I've successfully downloaded the Metamask Firefox Add-on, and imported my wallet into it. However I'm failing to see how I can use this add-on from within my DApp like I do on Chrome, using the ...
0
votes
0answers
24 views

“ SyntaxError: Unexpected end of JSON input” while interacting with smart contract using node instance

Im trying to interact with my smart contract using web3js. when i run js file using node instance i.e. node myfile.js Im getting error like undefined 1 SyntaxError: Unexpected end of JSON input ...
2
votes
2answers
27 views

USD Coin Balance Check By Web3

Now I am getting trouble on checking the USDC balance in my wallet address using web3. USDC is also said that it is ERC20 token, but when I checked the token contract ...
0
votes
1answer
18 views

What's the difference between web3.eth.personal and web3.eth.accounts?

I noticed that web3.eth.personal has unlockAccount method but not web3.eth.accounts. Why not? Is web3.eth.personal for personal or single account use while web3.eth.accounts for multiple accounts?
0
votes
0answers
22 views

Issue in setting GasPrice when sending raw transaction

I am using web3 and infura node to send my raw transaction but I am having difficulty in setting gasprice. I constructed rawtransaction as follows web3js.eth.getTransactionCount(myAddress, 'pending')...
0
votes
0answers
27 views

web3.eth.sign() problem [duplicate]

I am using infura and web3 0.20.0 in back-end.(nodejs, I don't want to interact with metamask(front-end)) Now, I am facing a problem. I tried to use ERC865. solidity function ...
0
votes
1answer
12 views

How to redirect to Etherscan website when transaction completes?

In my project, I am doing a transaction by using ethereum.send({ }) method from web3 in javascript using metamask. After the transaction completes I want to display the link to the user in label ...
1
vote
1answer
11 views

How to retrieve transaction hash value from the Promise object using web3js?

I'm trying to retrieve the transaction hash value after I call my smart contract method. My Promise object looks like below. returnPromise: Promise { "pending" } ​ <state>: "...
0
votes
1answer
19 views

Viewing transaction events by using web3 on geth console

According to https://web3py.readthedocs.io/en/stable/contracts.html#web3.contract.ContractEvents.myEvent web3 allows to extract the pertinent logs from a transaction receipt: tx_hash = contract....
0
votes
2answers
37 views

web3 1.0 events never fire

First off, my setup. System: ArchLinux Ganache: v2.0.0 (correction, v1.3.1) Solidity: 0.5.8 web3: 1.0.0-beta.37 (anything higher than 37, contract wont deploy) Node: 'latest' Some background and ...
0
votes
1answer
21 views

SyntaxError: await is only valid in async functions and async generators in web3js

Below is my code snippet. I wish to wait for the transaction hash value so that I can return my Javascript function with the hash value. But I get the error "SyntaxError: await is only valid in ...
0
votes
0answers
9 views

Web3NotFound Page rendering every time the drizzle-react DApp is refreshed

I'm trying to build a drizzle-react DApp. I want to implement a page called Web3NotFound.js which gets rendered when drizzle fails to find any web3 injected from MetaMask or Trust wallet browser. ...
0
votes
2answers
51 views

msg.sender in contract is empty

I have the following deployment script var contract = web3.eth.contract(response.abi); var bytecode = response.bytecode; var options = { from: ...
0
votes
0answers
27 views

How to grab a return value from a smart contract using web3js?

FYI, I'm a newbie. My smart contract method is below called buyToken. I'm using a Javascript code with web3 to execute the method. /// Requires the amount of Ether be at least or more of the ...