Getting Started with Polkadot Network

Tutorial 3 of 5

Getting Started with Polkadot Network

1. Introduction

In this tutorial, we'll discuss the Polkadot Network, an innovative multi-chain platform that enables different blockchains to interoperate seamlessly. By the end of this tutorial, you'll understand the structure of the Polkadot Network, how it enables efficient web structures, and how to interact with it using JavaScript libraries.

What You Will Learn

Basics of Polkadot Network
Interacting with Polkadot using JavaScript
Writing and deploying smart contracts on Polkadot

Prerequisites

Basic understanding of blockchain technology
Familiarity with JavaScript programming

2. Step-by-Step Guide

Polkadot's structure consists of a central Relay Chain which provides consensus and security for interconnected blockchains called parachains. For communication, Polkadot uses the Cross-Chain Message Passing (XCMP) protocol.

We will use the @polkadot/api, a JavaScript library to interact with Polkadot.

Installing @polkadot/api

Install the library using npm:

npm install @polkadot/api

Creating a Connection

The first step is creating a connection to a Polkadot node. Here's how you do it:

const { ApiPromise, WsProvider } = require('@polkadot/api');

async function main () {
  const wsProvider = new WsProvider('wss://rpc.polkadot.io');
  const api = await ApiPromise.create({ provider: wsProvider });

  console.log(api.genesisHash.toHex());
}

main().catch(console.error);

3. Code Examples

Here are some more examples of what you can do with the Polkadot JavaScript API.

Reading Chain Data

Here is how you can read the latest block header:

async function main () {
  //...
  const lastHeader = await api.rpc.chain.getHeader();
  console.log(`Last block #${lastHeader.number} has hash ${lastHeader.hash}`);
}

main().catch(console.error);

Writing Data

To submit a transaction, you need to have an account with some DOTs (Polkadot's native cryptocurrency). Here's an example of how to submit a transaction:

async function main () {
  //...
  const keyring = new Keyring({ type: 'sr25519' });
  const alice = keyring.addFromUri('//Alice');

  const transfer = api.tx.balances.transfer(bob.address, 12345);
  const hash = await transfer.signAndSend(alice);

  console.log('Transfer sent with hash', hash.toHex());
}

main().catch(console.error);

4. Summary

In this tutorial, we introduced the Polkadot Network and learned how to interact with it using the @polkadot/api JavaScript library. We read data from the blockchain and submitted a transaction.

Next Steps

To further your understanding, you should try setting up your own private Polkadot network, and deploying a smart contract on it.

Additional Resources

5. Practice Exercises

Write a script that prints the balance of a given account.
Write a script that submits a transfer from Alice to Bob, and then prints the new balances of both accounts.
Set up a private Polkadot network, and deploy a simple smart contract on it.

For solutions and further practice, refer to the Polkadot Wiki and JavaScript API documentation.