Storage Queries

Query on-chain storage

On-chain storage can be queried via client.query entry point. All the available storage entries for a chain are exposed in the ChainApi interface for that chain and can be executed with format: client.query.<pallet>.<storgeEntry>. E.g: You can find all the available storage queries of Polkadot network here, similarly for other networks as well.

// Query account balance
const balance = await client.query.system.account(<address>);

// Get all events of current block
const events = await client.query.system.events();

Subscribe to on-chain storage

You can also subscribe to on-chain storage changes by passing callback as the last argument to the storage query.

// Subscribe to account balance changes
const unsub = await client.query.system.account(<address>, (balance) => {
  console.log('New free balance', balance.data.free);

  unsub(); // unsubsribe from the subscription
});

// Subscribe to events of current best block
const unsub = await client.query.system.events((records) => {
  const transferEvent = client.events.balances.Transfer.find(records);
  
  if (transferEvent) {
    console.log('New transfer event: ', transferEvent);
    
    unsub(); // unsubsribe from the subscription
  }
});