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I am subscribing system events using the events api. After I got the specific event I am looking for, how should get the block hash of this event?

Thanks

api.query.system.events((events) => {
    console.log(`\nReceived ${events.length} events:`);

    // Loop through the Vec<EventRecord>
    events.forEach((record) => {
      const { event, phase } = record;

      // found the one
      if (event.section === 'SomeSection') {
          // notify user the block hash
      }
    });
  });
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  • More specifically I am listening to events fired by a chain bridge. I would like to notify the users of the block hash when their assets are arrived at the polkadot side of bridge. Aug 5, 2022 at 10:16

1 Answer 1

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There may be a simpler way to do this but here is a script:

import { ApiPromise, WsProvider } from '@polkadot/api';

export const getEvents = async () => {

    const wsProvider = new WsProvider('wss://rpc.polkadot.io');
    const api = await ApiPromise.create({ provider: wsProvider });
    await api.rpc.chain.subscribeNewHeads(async (header) => {
        console.log(`Chain is at block: #${header.number}`);
        const blockHash = await api.rpc.chain.getBlockHash(header.number);
        console.log(`blockHash: ${blockHash}`);
        const at = await api.at(blockHash);
        const events = await at.query.system.events();
        console.log(events.toHuman());
    });
}

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