eth_getFilterChanges | BNB Chain

BNB API polling method used to retrieve updates from a filter. A filter is an object used to track changes to the state of the blockchain.

Filters can be created using one of the following methods:

• eth_newFilter
• eth_newPendingTransactionFilter
• eth_newBlockFilter

After creating a filter using one of the available methods, the resulting filter ID can be used to fetch changes by calling the eth_getFilterChanges method.

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Parameters

• string — the filter ID of the filter for which you want to retrieve the changes

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Response

• array — an array that represents the changes that have occurred on the blockchain since the last time the filter was polled:
  • For filters created with eth_newBlockFilter:
    • blockHash — the hashes of the new blocks since the last time the filter was polled.
  • For filters created with eth_newPendingTransactionFilter:
    • transactionHash — the hashes identifying new pending transactions since the last time the filter was polled.
  • For filters created with eth_newFilter, the following event logs:
    • address — the contract address from which the event originated.
    • topics — an array of 32-byte data fields containing indexed event parameters.
    • data — the non-indexed data that was emitted along with the event.
    • blocknumber — the block number in which the event was included. null if it is pending.
    • transactionhash — the hash of the transaction that triggered the event. null if pending.
    • transactionindex — the integer index of the transaction within the block’s list of transactions. null if it is pending.
    • blockhash — the hash of the block in which the event was included. null if it is pending.
    • logindex — the integer identifying the index of the event within the block’s list of events. null if pending.
    • removed — the boolean value indicating if the event was removed from the blockchain due to a chain reorganization. True if the log was removed. False if it is a valid log.

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eth_getFilterChanges code examples

const ethers = require('ethers');
const NODE_URL = "CHAINSTACK_NODE_URL";
const provider = new ethers.JsonRpcProvider(NODE_URL);

async function getFilterChanges(filter) {
  try {
    const changes = await provider.send('eth_getFilterChanges', [filter]);
    console.log(changes); // Log the with the new data
  } catch (err) {
    console.error(err); // Handle errors that may occur
  }
}

const filterId =  '0x4e7ef166cd43f188b0f8f9e218966a8f' //'YOUR_FILTER_iD'
getFilterChanges(filterId)

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Use case

The eth_getFilterChanges method can poll a filter to periodically retrieve new data. You can, for example, create a blocks filter using eth_newBlockFilter and periodically poll it to get new blocks.