eth_newFilter | Cronos

Cronos API method that generates a filter object based on the filter parameters. It returns a filter ID, which can be used to retrieve the filter results using the eth_getFilterChanges method. By creating a filter for specific events, developers can receive notifications when those events occur and use them to trigger actions in their applications.

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Parameters

• object — the filter parameters:
  • fromBlock — (optional, default: latest) integer that specifies the starting block number from which the logs should be fetched.
  • toBlock — (optional, default: latest) integer that specifies the ending block number until which the logs should be fetched.
  • address — (optional) the contract address from which the logs should be fetched. It can be a single address or an array of addresses.
  • topics — (optional) an array of DATA topics. The event topics for which the logs should be fetched. It can be a single topic or an array of topics.
  • blockhash — (optional) the hash of the specific block. Limits logs to a specific block with a 32-byte hash value. It takes precedence over fromBlock and toBlock.

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Possible tags for fromBlock and toBlock

• latest — the most recent block in the blockchain and the current state of the blockchain at the most recent block.
• safe — the block that received justification from the beacon chain. Although this block could be involved in a chain reorganization, it would necessitate either a coordinated attack by the majority of validators or an instance of severe propagation latency.
• finalized — the block accepted as canonical by more than 2/3 of the validators. A chain reorganization is extremely unlikely, and it would require at least 1/3 of the staked ETH to be burned.
• earliest — the earliest available or genesis block.
• pending — the pending state and transactions block. The current state of transactions that have been broadcast to the network but have not yet been included in a block.

See the default block parameter and How The Merge Impacts Ethereum’s Application Layer.

Response

• result — a hexadecimal string representing the ID of the newly created filter

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The filters created are stored on the blockchain client instance. The filter is automatically deleted if not polled within a certain time (5 minutes by default).

Use the following methods with the filter ID:

• eth_getFilterChanges to retrieve updated logs
• eth_uninstallFilter to remove the filter

eth_newFilter code examples

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Note that the web3.eth.filter methods have been deprecated and replaced with the web3.eth.subscribe in web3.js. See web3.js subscriptions.

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

const filter = {
  toBlock: 'latest',
  address: '0x5C7F8A570d578ED84E63fdFA7b1eE72dEae1AE23',
  topics: ['0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef']
};

const createFilter = async () => {
  try {
    const filterId = await provider.send('eth_newFilter', [filter]);
    console.log(filterId); // the filter ID returned by eth_newFilter
    return filterId
  } catch (error) {
    console.log(error);
  }
};

createFilter();

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

const filter = {
  toBlock: 'latest',
  address: '0x5C0x5C7F8A570d578ED84E63fdFA7b1eE72dEae1AE23'
  topics: ['0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef']
};

const createFilter = async () => {
  try {
    const filterId = await provider.send('eth_newFilter', [filter]);
    console.log(filterId); // the filter ID returned by eth_newFilter
    return filterId
  } catch (error) {
    console.log(error);
  }
};

createFilter();

Use case

You can use eth_newFilter to create a filter for a specific action on a smart contract, for example, to monitor the transfer transactions from the Wrapped CRO token.

The idea is to create a filter using the eth_newFilter method to monitor an ERC-20 smart contract, WCRO in this case.

Try the eth_newFilter RPC method yourself