Havven-js NPM | npm.io

HavvenJs library

The Havven-JS Library provides a simple pre-packaged API to communicate with the Havven payment engine on ethereum. You can use it to build your own dApp that needs to work with payments using a stablecoin.

This is particularly useful for hackathon teams to quickly npm install havven-js and have stable payments integrated into their dApp in just a few minutes.

Under the hood, HavvenJs uses ethers.js library and its concept of providers and transaction signers.

The two main packages to do stable payments with are:

StablePayments - for transfer() and payment related functions like transfer()
Util - a bunch of handy utility functions for number handling and gas estimation

Some other packages for hacking with:

IsssuanceController - for Token swapper/exchange functions such as ETH > HAV & ETH > nUSD
Mintr - if you want to build a dApp for minting and burning stablecoins.

What can I build on the Havven payment engine?

Anything you can think of with programmable money. We provide the stability-as-a-service and soon fx (foreign exchange) with havvens multicurrency release.

We’ve come up with some thought starters for dApps you could create by integrating Havven’s stable payments into your projects.

Crypto Games - lottery, poker, fomoNUSD, nUSDCrash for kicks.
Crypto Ecommerce
Crypto Loans
Crypto Insurance
Crypto Payroll
Crypto Global Remittance

Install via npm

npm install havven-js

Example for getting the total nUSD stablecoin in circulation

const { HavvenJs } = require('havven-js');
const havjs = new HavvenJs(); //uses default ContractSettings - ethers.js default provider, mainnet
(async function() {
  const totalNUSD = await havjs.Nomin.totalSupply();
  const havTotalSupply = havjs.utils.formatEther(totalNUSD);
  console.log('nUSDTotalSupply', havTotalSupply);
})();

Default settings don't use any signer. That means that constants can be viewed from the contract but executing a transaction will fail. To execute transactions, set up signer.

4 signers are included in the library - Metamask (compatible with Dapp browsers), Trezor, Ledger and PrivateKey. Custom ethers.js compatible signers can be used too.

Example using a metamask signer

const { HavvenJs } = require('havven-js');
const metaMaskSigner = new HavvenJs.signers.Metamask();
const havjs = new HavvenJs({signer: metaMaskSigner}); //uses Metamask signer and default infura.io provider on mainnet

Example converting ETH to USD pegged stablecoin nUSD

Obtain test ETH from a faucet https://gitter.im/kovan-testnet/faucet

const txObj = await havjs.IssuanceController.exchangeEtherForNomins({ value: havjs.util.parseEther("0.123") });

Example of making a stablecoin payment

//Transfer stablecoins to any ethereum address, wallet or smart contract
const txObj = await havjs.StablePayments.transfer('0x5C545CA7f9D34857664FDCe6aDC22edcF1D5061f', nUSDReceived);

Example of minting stablecoin(nUSD) with private key signer

const { HavvenJs } = require('havven-js');
//parameters: default provider, default networkId, private key as a string
const signer = new HavvenJs.signers.PrivateKey(null, 0, '0x0123456789012345678901234567890123456789012345678901234567890123');
const havjs = new HavvenJs({signer});

async function run(){
  const totalSupply = await havjs.Havven.totalSupply();
  const havTotalSupply = havjs.utils.formatEther(totalSupply);
  console.log('havTotalSupply', havTotalSupply);

  //issue 100 nomins (will throw if insufficient funds for gas)
  try {
    const txObj = await havjs.Havven.issueNomins(havjs.util.parseEther("100")); //execute transaction (requires gas)
    console.log('transaction hash', txObj.hash);
  } catch (e) {
    console.log(e);
  }
}

run();

See /__tests__ folder for more examples.