Getting Started: Node.js

Where: Blockchain

First up is the ChainDefinition interface of the blockchain we intend to connect with. This interface consists of the id to identify the blockchain and a url of an API endpoint the script can connect with. This part of the config informs the new Session how to connect with the blockchain, which in this example is going to be the Jungle 4 (Testnet).

const chain = {
  id: "73e4385a2708e6d7048834fbc1079f2fabb17b3c125b146af438971e90716c4d",
  url: "https://jungle4.greymass.com",
}

If you are unsure of what the id parameter should be for a specific blockchain, you can simply access the v1/chain/get_info endpoint of any API for that network.The chain_id parameter it returns in the response indicates what this value should be (example).

What: Account and Permission

The next bit of information the Session will need is the account name and permission to use. These can be defined as ordinary strings or be passed in as Name typed variables.

const accountName = "wharfkit1111"
const permissionName = "test"

For the purpose of this guide we are using the existing wharfkit1111 account and the test permission.

How: Wallet Plugin

The final piece of information the Session requires is how it will sign transactions, which in this example is with a PrivateKey embedded in the script, which is loaded into the WalletPluginPrivateKey plugin.

const privateKey = "5Jtoxgny5tT7NiNFp1MLogviuPJ9NniWjnU4wKzaX4t7pL4kJ8s"
const walletPlugin = new WalletPluginPrivateKey(privateKey)

The plugin will accept either the standard or WIF format private key.

IMPORTANT: Protect your private keys. Embedding private keys like this in scripts puts the account and all its tokens at risk. Never publish source code containing private keys in Github repositories or use this method of signing in applications where users can extract the private key information.

Defining the Action

To perform a basic token transfer on Jungle 4, the script will need to define the action. The script can do this by defining a variable and utilizing the raw action data format.

const transferAction = {
  account: "eosio.token",
  name: "transfer",
  authorization: [session.permissionLevel],
  data: {
    from: session.actor,
    to: "wharfkittest",
    quantity: "0.0001 EOS",
    memo: "Hello World!",
  },
}

In this example, the transferAction variable is being set to an object that defines:

• The account in which the smart contract is deployed, which is eosio.token.
• The name of the action to perform on the contract, being transfer.
• The authorization array which defines which accounts permit this action, which we pass in session.permissionLevel, so it matches the current Session.
• The data object, which defines the parameters required by the smart contract.

For the eosio.token contract and its transfer action, the required parameters consist of:

• from: Which account is sending the tokens, in this case the session.actor.
• to: Which account is receiving the tokens, which we set to wharfkittest (another test account).
• quantity: The amount of tokens to send using the Asset format.
• memo: An optional memo to publicly provide additional information about the transfer.

Every smart contract will utilize different parameters for the data field to define the required parameters. Check the smart contract’s source code or its ABI to determine what these fields are, or check out Wharf’s Contract Kit for easier methods of generating this field in the near future.

Executing the Transaction

With an action defined, the script can now call the transact() method on the Session instance to automatically perform the transaction. This method is an asynchronous call, so for the purposes of this script, we will need to wrap it as an async function, which can just be named main() and called immediately.

async function main() {
  const result = await session.transact({ action: transferAction })
  console.log(`Transaction was successfully broadcast!`)
  console.log(
    `Explorer Link: https://jungle4.eosq.eosnation.io/tx/${result.response.transaction_id}`
  )
}

main()

The session.transact() call will take in the action we defined, and using all of the configuration data it has, will assemble it into a full transaction and sign it using the local wallet plugin.

This example script will then log to the console that the transaction was successful and render out a link to a block explorer to verify the results.