Working with Smart contracts in Javascript

Working with Smart contracts in Javascript

• 1.
  Working with smart contractsin JS Mikhail Kuznetcov Amsterdam 2018
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  About
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  Agenda Introduction Smart contracts andDApps Developer tools and environment setup Demo Web3
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  Ethereum Vitalik Buterin, co-founder ofEthereum ● Open source ● Decentralised ● Features smart contract functionality
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  Ethereum network 2 1 EVM 2 distincttypes of accounts: ● User addres, funds ● Contract address, funds, code attached to it
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  What are SmartContracts? [..] A smart contract is a set of promises, specified in digital form, including protocols within which the parties perform on these promises. Nick Szabo, 1996 Real world examples: ● Pension or trust fund ● Network democracy, voting ● Assets exchange ● Investments, ICOs
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  SC example pragma solidity^0.4.16; import 'zeppelin-solidity/contracts/token/ERC20/StandardToken.sol'; // declaration contract TodoList { TodoItem[] public todoItems; // data objects struct TodoItem { bytes32 value; bool active; } // methods function addTodoItem(bytes32 _value) returns (bool success) { TodoItem memory todoItem; todoItem.value = _value; todoItem.active = false; todoItems.push(todoItem); return true; } function toggleTodoItem(uint index) returns (bool success) { if (index >= todoItems.length) return; bool newValue = !todoItems[index].active; todoItems[index].active = newValue; return newValue; } Solidity PL
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  SC lifecycle Solidity code Compile ABI Bytecode Deploy Address `0x56f…` Interact Functions Events Blockchainnetwork
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  DApps stack Blockchain Ethereum platform Smartcontracts DApps
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  DApp JS workflowwith Web3 // init, using provide of your choice web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545")) //set defaults web3.eth.defaultAccount = '0x8888f1f195afa192cfee860698000c030f4c9db1' //do stuff if(web3.isConnected() && web3.isAddress(SOME_ADDRES)) { const balance = web3.eth.getBalance(SOME_ADDRES) web3.eth.sendTransaction(TRANSACTION, onSuccess) } Web3
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  Connecting to thenetwork JS setup: Ganache CLI (former ethereumjs-testrpc) Local test network as simple as: $: npm install -g ganache-cli $: ganache-cli <args> … or use GUI runner
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  Truffle workflow $: npminstall -g truffle $: mkdir myproject && cd myproject $: truffle init Blockchain sol sol sol Tuffle Web3 $: truffle compile $: truffle migrate [--reset] $: truffle console On contract change Setup DApp
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  ĐApp interaction withcontract Transaction SC validation Mining Costs New block Verification and execution on other nodes Blockchain network DApp UI interaction New status in UI
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  Demo ● Setup anddeploy ToDo list app, based on blockchain and smart contracts. https://github.com/mbeaudru/ethereum-todolist ● Extend functionality of a contract and app UI
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  Further steps Oraclize.it ● IDE,Remix ● Collections of tested and reusable contract blocks ● External events triggers ● Various libs bindings
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  Questions! QR code here