eth_newPendingTransactionFilter | Polygon

Polygon API method that creates a filter that listens for new pending transactions on the blockchain. Chainstack Polygon reference.

POST /0615fdf3c9eaf0681469e61a4308ea09

eth_newPendingTransactionFilter

cURL

curl --request POST \
  --url https://polygon-mainnet.core.chainstack.com/0615fdf3c9eaf0681469e61a4308ea09 \
  --header 'Content-Type: application/json' \
  --data '
{
  "jsonrpc": "2.0",
  "method": "eth_newPendingTransactionFilter",
  "params": [],
  "id": 1
}
'

200

{
  "jsonrpc": "<string>",
  "id": 123,
  "result": [
    "<string>"
  ]
}

Polygon API method that creates a filter that listens for new pending transactions on the blockchain. It returns a filter ID, which can be used to retrieve the results using the eth_getFilterChanges method. The eth_newPendingTransactionFilter method is useful for developers who must be notified of new pending transactions in real time.

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Parameters

• none

Response

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

Code examples

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 updates
• eth_uninstallFilter to remove the filter

eth_newPendingTransactionFilter code examples

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

ethers.js

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

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

createFilter();

Use case

One way to use the eth_newPendingTransactionFilter method is to listen for new pending transactions at predefined intervals and extract specific data from them. For instance, a decentralized application might check for pending transactions every second and identify those that transfer a value greater than a certain amount of the MATIC token. This could be useful for monitoring high-value transactions or detecting potential fraud or security threats in real time.

Here is an implementation of this concept using ethers.js:

index.js

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

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

// Use the filter to extract the value from each transaction
async function getValue(filter) {
  try {
    // Retrieve the list of new pending transactions
    const transactions = await provider.send('eth_getFilterChanges', [filter]);

    // Loop through the list of transactions and process each one
    for (const hash of transactions) {

      const receipt = await provider.send("eth_getTransactionByHash", [hash]);

      // Check that the receipt is not null and has a non-null value field
      if (receipt && receipt.value != null) {
        const value = receipt.value;
        const decimalValue = BigInt(value).toString();
        const convertedValue = ethers.utils.formatEther(decimalValue);
        
        // Check if the transferred value is greater than or equal to 100 Matic
        if (convertedValue >= 100) {
          console.log(`This transaction is sending more than 100 Matic`);
          console.log(`Transaction Hash: ${hash}`);
          console.log(`Value transferred: ${convertedValue} \n`);
        }
      }
    }
  } catch (error) {
    console.error(error); // Handle errors that may occur
  }
}

// Main program setting an interval to call the `getValue` function at regular intervals
async function main() {

const filterId =  await createFilter();
setInterval(getValue, 1000, filterId);

}

main()

This code sets up an Ethereum filter to listen for new pending transactions and extract specific data from them.

The code consists of three functions: createFilter, getValue, and main. Here’s an overview of how each function works:

The createFilter function sets up a new filter using the eth_newPendingTransactionFilter method. It returns the ID of the filter, which can be used to retrieve data from the filter later.

The main function sets up the program by first calling the createFilter function to create a new filter and retrieve its ID. It then sets an interval to call the getValue function every 1 second, passing the filter ID as an argument to retrieve the latest transaction data at regular intervals.

Body

application/json

jsonrpc · string · default: 2.0

method · string · default: eth_newPendingTransactionFilter

params · array

id · integer · default: 1

Response

200 - application/json

The new filter ID.

jsonrpc · string

id · integer

result · string[]