Polkadot JS API Crash Course

`api`

import { ApiPromise, WsProvider } from "@polkadot/api";
const provider = new WsProvider("wss://rpc.polkadot.io");
const api = await ApiPromise.create({ provider });

api.stats;
api.runtimeVersion;
api.isConnected;

`api.registry`

api.registry.chainDecimals;
api.registry.chainTokens;
api.registry.chainSS58;

<p>api.registry.metadata;
api.registry.metadata.pallets.map(p => p.toHuman());</p>
api.registry.createType();

`api.rpc`

Can call into all RPC endpoints of the chain. All endpoints are divided based on on scope and method, such as scope_method, e.g. system_chain.

api.rpc.chain.getBlock()

<p>api.rpc.system.health()
await api.rpc.system.version()</p>
<p>await api.rpc.state.getRuntimeVersion()
await api.rpc.state.getPairs("0x")</p>
await api.rpc.state.getKeysPaged("0x", 100)
await api.rpc.state.getStorage()
<a href="https://polkadot.js.org/docs/substrate/rpc#getstoragekey-storagekey-at-blockhash-storagedata">https://polkadot.js.org/docs/substrate/rpc#getstoragekey-storagekey-at-blockhash-storagedata</a>
await api.rpc.state.getStorageSize("0x3A636F6465"),

`Keyring`

import KeyringPair from "@polkadot/keyring";
import { Keyring } from "@polkadot/api";
const kr = new Keyring({ type: "sr25519", ss58Format: 42 });
const account = kr.addFromUri("evil danger film ship lamp gorilla wear job despair garbage dial repair");

let sig = account.sign(new Uint8Array([1, 2, 3]));
account.verify(new Uint8Array([1, 2, 3]), sig, account.publicKey);

`api.tx`

let call = api.tx.balances.transfer("5FUDdxaaZfye6ogJgqHh3Usqd6WN6q8aApFH4XNjU9iDvC49", 1000000000000);
call.toHuman();
const signed = call.sign(account);
call.toHuman();

<p>signed.send();
signed.send();</p>
<p>await call1.signAndSend(account, ({ events = [], status, dispatchError }) => {
  console.log(status.toHuman());
});</p>
call
  .paymentInfo(account)(await api.rpc.payment.queryInfo(call.toHex()))
  .toHuman();

Types

createTypeA powerful tool to keep in mind.
everything is Codec by default, and has toHuman, toU8a, toHex, toString and .eq.

import * as BN from "bn.js";
api.createType("Balance", new Uint8Array([1, 2, 3, 4]));

Crypto Utils

import { blake2AsHex, xxHashAsHex, checkAddress } from "@polkadot/util-crypto";
blake2AsHex("Foo");
xxHashAsHex("Foo");

`api.query`

api.query.[module_name].[storage_name]()
api.query.[module_name].[map_name](key)
api.query.[module_name].[map_name].entries()
api.query.[module_name].[double_map_name](key1, key2)

await api.query.system
  .number()(await api.query.system.lastRuntimeUpgrade())
  .toHuman()(await api.query.council.members())
  .toHuman();

// let's see what else a storage item has
api.query.council.proposalOf;
api.query.council.proposalOf
  .keyPrefix()(await api.query.council.proposalOf.entries())
  .forEach(([key, value]) => console.log(`${key} // ${value}`))(await api.query.council.proposalOf.entries())
  .forEach(([key, value]) => console.log(`${key} // ${key.args[0]} // ${key.slice(-32)} // ${value}`));
await api.query.council
  .proposalOf("0x678debcc07e2300db98fa74979c8e75ebd0075bee8f58bf7c1ca4bda724449f8")(
    await api.query.council.proposalOf.keys()
  )
  .map(x => x.toString());

`api.consts`

api.consts.[config_name]()

api.consts.system.version.toHuman();
api.consts.system.blockWeights.toHuman();
api.consts.system.blockLength.toHuman();

`api.derive`

Helpers that combine multiple calls and queries into one. Entirely optional to use.

await api.derive.accounts.hasIdentity("15S7YtETM31QxYYqubAwRJKRSM4v4Ua6WGFYnx1VuFBnWqdG");
const unsub = await api.derive.chain
  .subscribeNewHeads(h => {
    console.log(h.author);
    unsub();
  })(await api.rpc.chain.getBlockHash(100))
  .toHuman()(await api.rpc.chain.getBlock("0xedf9246b378fe4aa1c29d21c64b0bf9880553690ce6cd956c18c03310e49fa5f"))
  .toHuman();
api.derive.chain.getBlockByNumber(1000);

api.derive.chain.bestNumberFinalized();

Exercise: Using Polkadot JS API

Find the some interesting blocks in Polkadot/Kusama:
- The largest block
- The block that consumed the most weight.
- Last remark that Shawn made onchain??? 🤔
Bonus: use subxt.

Polkadot JS API Crash Course

Context

Overview

Overview

Overview

`api`

`api.registry`

`api.rpc`

`Keyring`

`api.tx`

Types

Crypto Utils

`api.query`

`api.consts`

`api.derive`

Exercise: Using Polkadot JS API