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JavaScript API libraries

In order for a web app to interact with the Xphere blockchain (i.e. read blockchain data and/or send transactions to the network), it must connect to a Xphere node.

For this purpose, every Xphere client implements the JSON-RPC specification, so there are a uniform set of methods that applications can rely on.

If you want to use JavaScript to connect with a Xphere node, it's possible to use vanilla JavaScript but several convenience libraries exist within the ecosystem that make this much easier. With these libraries, developers can write intuitive, one-line methods to initialize JSON-RPC requests (under the hood) that interact with Xphere.

Please note that for running a node, it's essential to ensure your node includes all necessary components for proper operation. If your node is not on your local machine (e.g. your node is running on an AWS instance), update the IP addresses in the tutorial accordingly. For more information, please see our page on running a node.

Prerequisites​

As well as understanding JavaScript, it might be helpful to understand the Xphere stack and Xphere clients.

Why use a library?​

These libraries abstract away much of the complexity of interacting directly with a Xphere node. They also provide utility functions (e.g. converting XPH to smaller units) so as a developer you can spend less time dealing with the intricacies of Xphere clients and more time focused on the unique functionality of your application.

Library features​

Connect to Xphere nodes​

Using providers, these libraries allow you to connect to Xphere and read its data, whether that's over JSON-RPC, XphereScan, or other supported services.

Ethers example

// A BrowserProvider wraps a standard Web3 provider, which is
// injected into each page
const provider = new ethers.BrowserProvider(window.ethereum);

// Sign transactions to send XPH and change the state within the blockchain
const signer = provider.getSigner();

Web3js Example

var web3 = new Web3("http://localhost:8545");
// or
var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

// Change provider
web3.setProvider("ws://localhost:8546");
// or
web3.setProvider(new Web3.providers.WebsocketProvider("ws://localhost:8546"));

// Using the IPC provider in Node.js
var net = require("net");
var web3 = new Web3(
  new Web3.providers.IpcProvider("/Users/myuser/Library/Xphere/geth.ipc", net)
);
// On Windows: "\\\\.\\pipe\\xphere.ipc"
// On Linux: "/users/myuser/.xphere/geth.ipc"

Once set up you'll be able to query the blockchain for:

  • block numbers
  • gas estimates
  • smart contract events
  • network id
  • and more...

Wallet functionality​

These libraries give you functionality to create wallets, manage keys and sign transactions.

Here's an examples from Ethers

// Create a wallet instance from a mnemonic...
mnemonic =
  "announce room limb pattern dry unit scale effort smooth jazz weasel alcohol";
walletMnemonic = Wallet.fromPhrase(mnemonic);

// ...or from a private key
walletPrivateKey = new Wallet(walletMnemonic.privateKey);

walletMnemonic.address === walletPrivateKey.address;
// true

// The address as a Promise per the Signer API
walletMnemonic.getAddress();
// { Promise: '0x71CB05EE1b1F506fF321Da3dac38f25c0c9ce6E1' }

// A Wallet address is also available synchronously
walletMnemonic.address;
// '0x71CB05EE1b1F506fF321Da3dac38f25c0c9ce6E1'

// The internal cryptographic components
walletMnemonic.privateKey;
// '0x1da6847600b0ee25e9ad9a52abbd786dd2502fa4005dd5af9310b7cc7a3b25db'
walletMnemonic.publicKey;
// '0x04b9e72dfd423bcf95b3801ac93f4392be5ff22143f9980eb78b3a860c4843bfd04829ae61cdba4b3b1978ac5fc64f5cc2f4350e35a108a9c9a92a81200a60cd64'

// The wallet mnemonic
walletMnemonic.mnemonic;
// {
//   locale: 'en',
//   path: 'm/44\'/60\'/0\'/0/0',
//   phrase: 'announce room limb pattern dry unit scale effort smooth jazz weasel alcohol'
// }

// Note: A wallet created with a private key does not
//       have a mnemonic (the derivation prevents it)
walletPrivateKey.mnemonic;
// null

// Signing a message
walletMnemonic.signMessage("Hello World");
// { Promise: '0x14280e5885a19f60e536de50097e96e3738c7acae4e9e62d67272d794b8127d31c03d9cd59781d4ee31fb4e1b893bd9b020ec67dfa65cfb51e2bdadbb1de26d91c' }

tx = {
  to: "0x8ba1f109551bD432803012645Ac136ddd64DBA72",
  value: utils.parseEther("1.0"),
};

// Signing a transaction
walletMnemonic.signTransaction(tx);
// { Promise: '0xf865808080948ba1f109551bd432803012645ac136ddd64dba72880de0b6b3a7640000801ca0918e294306d177ab7bd664f5e141436563854ebe0a3e523b9690b4922bbb52b8a01181612cec9c431c4257a79b8c9f0c980a2c49bb5a0e6ac52949163eeb565dfc' }

// The connect method returns a new instance of the
// Wallet connected to a provider
wallet = walletMnemonic.connect(provider);

// Querying the network
wallet.getBalance();
// { Promise: { BigNumber: "42" } }
wallet.getTransactionCount();
// { Promise: 0 }

// Sending xp
wallet.sendTransaction(tx);

Read the full docs

Once set up you'll be able to:

  • create accounts
  • send transactions
  • sign transactions
  • and more...

Interact with smart contract functions​

JavaScript client libraries allow your application to call smart contract functions by reading the Application Binary Interface (ABI) of a compiled contract.

The ABI essentially explains the contract's functions in a JSON format and allows you to use it like a normal JavaScript object.

So the following Solidity contract:

contract Test {
    uint a;
    address d = 0x12345678901234567890123456789012;

    function Test(uint testInt)  { a = testInt;}

    event Event(uint indexed b, bytes32 c);

    event Event2(uint indexed b, bytes32 c);

    function foo(uint b, bytes32 c) returns(address) {
        Event(b, c);
        return d;
    }
}

Would result in the following JSON:

[{
    "type":"constructor",
    "payable":false,
    "stateMutability":"nonpayable"
    "inputs":[{"name":"testInt","type":"uint256"}],
  },{
    "type":"function",
    "name":"foo",
    "constant":false,
    "payable":false,
    "stateMutability":"nonpayable",
    "inputs":[{"name":"b","type":"uint256"}, {"name":"c","type":"bytes32"}],
    "outputs":[{"name":"","type":"address"}]
  },{
    "type":"event",
    "name":"Event",
    "inputs":[{"indexed":true,"name":"b","type":"uint256"}, {"indexed":false,"name":"c","type":"bytes32"}],
    "anonymous":false
  },{
    "type":"event",
    "name":"Event2",
    "inputs":[{"indexed":true,"name":"b","type":"uint256"},{"indexed":false,"name":"c","type":"bytes32"}],
    "anonymous":false
}]

This means you can:

  • Send a transaction to the smart contract and execute its method
  • Call to estimate the gas a method execution will take when executed in the EVM
  • Deploy a contract
  • And more...

Utility functions​

Utility functions give you handy shortcuts that make building with xphere a little easier.

ETH values are in Wei by default. 1 ETH = 1,000,000,000,000,000,000 WEI – this means you're dealing with a lot of numbers! web3.utils.toWei converts ether to Wei for you.

And in ethers it looks like this:

// Get the balance of an account (by address or ENS name)
balance = await provider.getBalance("ethers.eth");
// { BigNumber: "2337132817842795605" }

// Often you will need to format the output for the user
// which prefer to see values in ether (instead of wei)
ethers.utils.formatEther(balance);
// '2.337132817842795605'