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![What are Smart Contracts?
[..] 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](https://image.slidesharecdn.com/smartcontractsinjs-180329121810/85/Working-with-Smart-contracts-in-Javascript-6-320.jpg)
![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](https://image.slidesharecdn.com/smartcontractsinjs-180329121810/85/Working-with-Smart-contracts-in-Javascript-7-320.jpg)
![Truffle workflow
$: npm install -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](https://image.slidesharecdn.com/smartcontractsinjs-180329121810/85/Working-with-Smart-contracts-in-Javascript-12-320.jpg)
![What are Smart Contracts?
[..] 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](https://image.slidesharecdn.com/smartcontractsinjs-180329121810/75/Working-with-Smart-contracts-in-Javascript-6-2048.jpg)
![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](https://image.slidesharecdn.com/smartcontractsinjs-180329121810/75/Working-with-Smart-contracts-in-Javascript-7-2048.jpg)
![Truffle workflow
$: npm install -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](https://image.slidesharecdn.com/smartcontractsinjs-180329121810/75/Working-with-Smart-contracts-in-Javascript-12-2048.jpg)
Uploaded byMikhail Kuznetcov
Working with Smart contracts in Javascript
This document provides an overview of smart contracts and developing decentralized applications (DApps) using JavaScript and Ethereum. It discusses smart contracts, the Ethereum network, developing and deploying smart contracts with Solidity, interacting with smart contracts from DApps using Web3.js, and demonstrates a todo list DApp. The document also briefly mentions further topics like Oraclize and the Remix IDE.
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Working with Smart contracts in Javascript
- 1. Working with smart contractsin JS Mikhail Kuznetcov Amsterdam 2018
- 2.
- 3. Agenda Introduction Smart contracts andDApps Developer tools and environment setup Demo Web3
- 4. Ethereum Vitalik Buterin, co-founder ofEthereum ● Open source ● Decentralised ● Features smart contract functionality
- 5. Ethereum network 2 1 EVM 2 distincttypes of accounts: ● User addres, funds ● Contract address, funds, code attached to it
- 6. 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
- 7. 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
- 8.
- 9. DApps stack Blockchain Ethereum platform Smartcontracts DApps
- 10. 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
- 11. 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
- 12. 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
- 13. 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
- 14. 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
- 15. Further steps Oraclize.it ● IDE,Remix ● Collections of tested and reusable contract blocks ● External events triggers ● Various libs bindings
- 16.