Programming Ethereum smart contract transactions in JavaScript
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By Mikko Ohtamaa a year ago. Tagged under web3ethereumjavascriptdappgethparitywebpacknodejssoliditysolc. This a tutorial blog post and web application showing how to deploy an Ethereum smart contract and transacting with this contract from a web user interface. The web application written using JavaScript, React user interface library and Web3 ethereum npm theming.
The production web application communicates with Ethereum blockchain using Etherscan. View the example application source code on Github. You need to be comfortable in advanced JavaScript programming. You need to have geth Go-Ethereum node or any Ethereum node software running in a Ethereum Ropsten testnet. See below how to install and connect to one safely. You need to be comfortable working on a command line in UNIXy environment, though Windows works also. You need to have solc installed.
Clone the Github repository. Install Node version 7. Use nvm script to make this easy for you. This demostration is built Ethereum Ropsten testnet in mind. The public testnet is ideal for cases where you don't want to spend any money to test web3 ethereum npm contracts, but you still want to share them publicly and use public blockchain explorers to debug your contracts.
Note that running a private testnet usin geth is still much faster alternative, transaction web3 ethereum npm wise, compared to the public testnet. See here how to deploy geth securely on a server and then build a SSH tunnel from your local development computer to server running geth. A private key is just a bit number. You can generate one easily web3 ethereum npm a passphrase using sha3 hash in node console.
See my demo transaction in Etherscan Ropsten explorer. You can skip this step if you want as there is already a deployed test contract here. See a sample deployed web3 ethereum npm. Now when your contract is deployed, you have a private key to your account, you have your Etherscan. Either run the app locally below or directly use the hosted version.
The transaction is constructed offline using contract address, private key, nonce and function description web3 ethereum npm here. The raw transaction web3 ethereum npm is pushed to Ethereum network over EtherScan.
The transaction web3 ethereum npm also carry value as ETH that get added to the ethers hold by the smart contract itself. Each transaction has a cost in gas.
More complex your transaction is, more code Web3 ethereum npm Virtual Machine runs and more data you store on the blockchain, more gas you need to pay in ETH as a transaction cost. It's a safety limit. All unused gas and related ETH is credited back to your Ethereum account. There is also a gas price associated with the transaction gas. More you are willing to pay for the gas, more likely miners pick up your transaction.
For normal blockchain usage, you usually never need to change the gas price. If you wish to edit this application web3 ethereum npm use it as a starting point for your own product you can run WebPack automatically reloading development server locally:. TokenMarket provides a complete service for creating tokens, developing and auditing smart contracts, crowd-sale hosting and an web3 ethereum npm list of other services. Introduction This a tutorial blog post and web application showing how to deploy an Ethereum smart contract and transacting with this contract from a web user interface.
We use both command line Node. View demo You can view and try the demo application here: Prerequisites You need to be comfortable in advanced JavaScript programming.
See here how to deploy geth securely on a server and then build a SSH web3 ethereum npm from your local development computer to server running geth See another blog post how to set up geth with password protected JSON RPC Creating a private key The web3 ethereum npm app has a text input that directly takes your Ethereum account private key.
Connect to your geth and send some balance from geth coinbase address to this address: Creating a smart contract We use the following sample smart contract for the demo: Developing app locally If you wish to edit this application and use it as a starting point for your own product you can run WebPack automatically reloading development server locally: Here is an example:
