Getting started

Installation

1. Install dependencies:

   npm install

2. Copy the example environment file and provide your HGraph API key:

   cp .env.example .env
   # Edit .env and replace <YOUR_API_KEY> with your key

Building

Compile the TypeScript source into the dist directory:

npm run build

Running the application

Execute the compiled code directly:

node dist/index.js
# or
npm run start

When successful you should see output similar to:

consensus_timestamp was about <seconds> seconds ago

Environment variables

• HGRAPH_API_KEY – your API key used by the GraphQL client. This value is loaded from .env at runtime.

GraphQL client usage

src/index.ts demonstrates subscribing to the latest transaction using @hgraph.io/sdk:

const LatestTransactionSubscription = `
subscription LatestTransaction {
  transaction(limit: 1, order_by: {consensus_timestamp: desc}) {
    consensus_timestamp
  }
}`

const subscription = client.subscribe(LatestTransactionSubscription, {
  next: ({ data }) => {
    const { consensus_timestamp } = data.transaction[0]
    const diff = secondsSinceConsensus(consensus_timestamp, BigInt(Date.now()))
    console.log(`consensus_timestamp was about ${diff} seconds ago`)
  }
})

If you encounter connection errors ensure the API key is valid and that your network allows outbound connections to HGraph.

Detecting contract type

src/contractType.ts shows how to determine if a contract address implements the ERC-20 or ERC-721 interface using ethers. The exported detectContractType function returns "erc20", "erc721", or "unknown". The file also contains showContractTypeDemo which downloads token lists from the Hiero Mirror Node Explorer repository and prints the detected type of a couple of sample addresses.

Run the demo with:

npm run demo:contractType

ERC wrapper examples

Run the following command to build the project and execute a script demonstrating every function in the ERC20 and ERC721 wrappers:

npm run start:wrappers

The script src/ercWrappersDemo.ts shows how to read token information and invoke transfer functions using an ethers Wallet.