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

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Prerequisites

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

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Why use a library?

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

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Library features

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Connect to Parallax nodes

Using providers, these libraries allow you to connect to Parallax and read its data, whether that’s over JSON-RPC or MetaMask. Ethers example 
// A Web3Provider wraps a standard Web3 provider, which is
// what MetaMask injects as window.ethereum into each page
const provider = new ethers.providers.Web3Provider(window.ethereum)

// The MetaMask plugin also allows signing transactions to
// send laxes and pay to change state within the blockchain.
// For this, we need the account signer...
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("/Users/myuser/Library/Parallax/prlx.ipc", net) // mac os path
// or
var web3 = new Web3(
  new Web3.providers.IpcProvider("/Users/myuser/Library/Parallax/prlx.ipc", net)
) // mac os path
// on windows the path is: "\\\\.\\pipe\\prlx.ipc"
// on linux the path is: "/users/myuser/.parallax/prlx.ipc"
Once set up you’ll be able to query the blockchain for:
  • block numbers
  • gas estimates
  • smart contract events
  • network id
  • and more…

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Wallet functionality

These libraries give you functionality to create wallets, manage keys and sign transactions. Here’s an example from Ethers 
// Create a wallet instance from a mnemonic...
mnemonic =
  "announce room limb pattern dry unit scale effort smooth jazz weasel alcohol"
walletMnemonic = Wallet.fromMnemonic(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 laxes
wallet.sendTransaction(tx)
Read the full docs↗ Once set up you’ll be able to:
  • create accounts
  • send transactions
  • sign transactions
  • and more…

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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 PVM
  • Deploy a contract
  • And more…

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Utility functions

Utility functions give you handy shortcuts that make building with Parallax a little easier. LAX values are in Wei by default. 1 LAX = 1,000,000,000,000,000,000 WEI – this means you’re dealing with a lot of numbers! web3.utils.toWei converts LAX 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'

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Available libraries

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Web3.js

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Ethers.js

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The Graph

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light.js

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Web3-wrapper

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Alchemyweb3

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Alchemy NFT API

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viem

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