Creating Type Safe DApps with Typescript and TypeChain

@krzkaczor

@ethereum_ts

"Javascript is pretty good language"

~ some JS devs

class Cat extends Animal {
  meow = async () => {
    console.log("returned promise of moewing");
  }
}

function main() {
  const cat = new Cat();
  cat.meow();
}

Modern Javascript

"Typescript is even a better language"

~ me

class Cat extends Animal {
  meow = async () => {
    console.log("returned promise of moewing");
  }
}

function main() {
  const cat = new Cat();
  cat.meow(); // floating promise detected!
}

Typescript = Javascript + types

function sum(a, b) {
  return a + b;
}

const four = sum(2,2);

function sum(a: number, b: number) {
  return a + b;
}

const four = sum(2,2);

TS's type system:

structural typing
advanced type level features (conditional types, mapped types)
entirely stripped out from the output
allows advanced refactoring

const MyContract = web3.eth.contract(abiArray);

// instantiate by address
const contractInstance = MyContract.at(address);

// call 
const result = await myContractInstance.myConstantMethod('myParam');

// tx
const resultTx = await myContractInstance.myStateChangingMethod('someParam1', 23, 
  {value: 200, gas: 2000});

Interacting with smart contracts using JS and Web3js

TypeChain

Typescript bindings for Ethereum smart contracts

ABI

TS wrapper

< demo >

Features

static typing
perfect IDE support for dapp development
multiple targets
- web3.js 0.20/1.0/2.0
- ethers
- truffle
custom targets

Why would you want to use it?

better DX
saves time
helps during migrations

Future

bypass ABIs limitation

ethereum-ts/TypeChain

THANKS!

@krzkaczor

https://github.com/ethereum-ts/TypeChain