Ethers.js – How to Listen for All Events of a Smart Contract with Ethers.js on Polygon

etherethers.jseventsnodejspolygon

What I would like to know is if there is a way to continuously listen for a single contract and fetch all the events emitted in real time. What I was able to find right now are ways of listening for only one event at a time in specific contract. To be more precise:
I have a smart contract deployed in polygon testnet (mumbai), this is an upgradable contract that is connected to other contracts and as usual it emits events that I would like to capture.
I use Alchemy as provider.
Another fact that is not clear to me is why in polyscan the method in the event is listed like 0x40c10f19 and not with the name.

I also try to use this code before asking you guys of how to do this:
`

filter = {
    address: CONTRACT_ADDRESS,
    topics:[
        utils.id("MarketItemCreated(address,uint256,address,uint256,uint256)"),
        utils.id("Transfer(address,address,address,uint256,uint256)")
    ]
}

provider.on(filter,(log,event)=>{
    console.log(log)
    console.log(event)
})

But when I actually interact with the contract I can't capture the events (the console.log does not display anything) but I can see the event in polyscan. I also try with by filtering only with the address without specifying the topic and I also try withproveder.once` but no way.

What am I doing wrong? or instead, What am I missing? every hints or contributions are appreciate 🙂

Best Answer

Hi developer advocate at Chainstack here!

Web3.js has a subscriprion method to easily to that!

const Web3 = require("web3");

const node_url = "CHAINSTACK_WSS_URL";
const web3 = new Web3(node_url)

var logs = web3.eth.subscribe("logs", {
        address: "CONTRACT_ADDRESS",
        topics: []
    }, function(error, result) {
        if (!error)
            console.log(result);
    })
    .on("connected", function(subscriptionId) {
        console.log(subscriptionId);
    })
    .on("data", function(log) {
        console.log(log);
    })
    .on("changed", function(log) {});

Remember that you need a web-socket endpoint to use subscriptions in web3.js.

You can find more examples in the Chainstack docs API reference, and in the web3.js docs.

I hope this helps you!

Update Responding To Comments Below

Here's a bit of code you to check out web3.eth.filter(...) with:

var filter = web3.eth.filter({ address: ["0xc4af56cd5254aef959d4bce2f75874007808b701"], fromBlock: 2615848, toBlock: "latest" });
var i = 0;
filter.watch(function (error, result) {
  console.log("RESULT: Filter " + i++ + ": " + JSON.stringify(result));
});
filter.stopWatching();

The results produce include:

RESULT: Filter 0: {"address":"0xc4af56cd5254aef959d4bce2f75874007808b701","blockHash":"0x201154027d3c69cca298fab9983848269eee04cc26a9e1e7f2d06c9e1529b8f5","blockNumber":2615921,"data":"0x2fd64880bc17977672b2e25fff32b433975c4004b4fbd094936429e92f58d39f000000000000000000000000a74476443119a942de498590fe1f2454d7d4ac0d00000000000000000000000000000000000000000000000000000000000186a0","logIndex":2,"removed":false,"topics":["0x242ddf37c1721f450a35afdb783ef36e84d032a300600da464ff17d600cceed7"],"transactionHash":"0x6a7f83c93837f4ab11e1bc9dae2a34df4b4610b0d87512e451a36b5f53fb9661","transactionIndex":17}
RESULT: Filter 1: {"address":"0xc4af56cd5254aef959d4bce2f75874007808b701","blockHash":"0x201154027d3c69cca298fab9983848269eee04cc26a9e1e7f2d06c9e1529b8f5","blockNumber":2615921,"data":"0x2fd64880bc17977672b2e25fff32b433975c4004b4fbd094936429e92f58d39f0000000000000000000000000020dba1d308339182239056a00fcc146d2e26e0000000000000000000000000399156ee3339f4b29a53e307b98cce09fda3bac7","logIndex":3,"removed":false,"topics":["0x2d6a3482be690073d89f3c5420f70aca9f53be93321c5f45b5be55907b5f2b5b"],"transactionHash":"0x6a7f83c93837f4ab11e1bc9dae2a34df4b4610b0d87512e451a36b5f53fb9661","transactionIndex":17}
RESULT: Filter 2: {"address":"0xc4af56cd5254aef959d4bce2f75874007808b701","blockHash":"0x58fd992519b8bb06b8a8cddac850efad4f2b3b8dd5069a0d0d8f4deb15616b81","blockNumber":2617375,"data":"0x2fd64880bc17977672b2e25fff32b433975c4004b4fbd094936429e92f58d39f0000000000000000000000000020dba1d308339182239056a00fcc146d2e26e0000000000000000000000000b362bba1c7c5c857e3ac74d740c0007c48db7362","logIndex":5,"removed":false,"topics":["0x2d6a3482be690073d89f3c5420f70aca9f53be93321c5f45b5be55907b5f2b5b"],"transactionHash":"0xb7ef581cd0e6597525e254add6f820ac6ecf860d89d01656035dfd880dac2747","transactionIndex":6}
...

The events above are the Golem Network Token (GNT) TokenTraderFactory with source code available from 0xc4af56cd5254aef959d4bce2f75874007808b701. You can find further information on this TokenTraderFactory at Trustless Golem Network Token (GNT) Selling Contract.

Note that the topics in the events above include the hex strings below:

0x242ddf37c1721f450a35afdb783ef36e84d032a300600da464ff17d600cceed7
0x2d6a3482be690073d89f3c5420f70aca9f53be93321c5f45b5be55907b5f2b5b

Here are the events declared in the TokenTraderFactory contract:

event TradeListing(bytes32 bookid, address owner, address addr);
event NewBook(bytes32 bookid, address asset, uint256 units);

In geth:

> web3.sha3('NewBook(bytes32,address,uint256)')
"0x242ddf37c1721f450a35afdb783ef36e84d032a300600da464ff17d600cceed7"
> web3.sha3('TradeListing(bytes32,address,address)')
"0x2d6a3482be690073d89f3c5420f70aca9f53be93321c5f45b5be55907b5f2b5b"

You will have to interpret the data fields by yourself. From the second listing above, the data is 0x2fd64880bc17977672b2e25fff32b433975c4004b4fbd094936429e92f58d39f0000000000000000000000000020dba1d308339182239056a00fcc146d2e26e0000000000000000000000000399156ee3339f4b29a53e307b98cce09fda3bac7

This can be separated into:

0x
2fd64880bc17977672b2e25fff32b433975c4004b4fbd094936429e92f58d39f
0000000000000000000000000020dba1d308339182239056a00fcc146d2e26e0
000000000000000000000000399156ee3339f4b29a53e307b98cce09fda3bac7

In the TokenTraderFactory event TradeListing(bytes32 bookid, address owner, address addr) event,

bookid = 0x2fd64880bc17977672b2e25fff32b433975c4004b4fbd094936429e92f58d39f
owner  = 0x0020dba1d308339182239056a00fcc146d2e26e0
addr   = 0x399156ee3339f4b29a53e307b98cce09fda3bac7

Etherscan – Querying Events Using Ethers.js Returns Logs with Unrelated Contract Addresses

The issue seems to stem from the differences between how getLogs() behaves in ethers v5 and ethers v6. This change in behavior isn't well-documented, leading to confusion.

For more precise and specific querying for contract events, ethers provides the queryFilter() method on a contract instance. This method is more intuitive for querying events and is the recommended approach.

Here's a code snippet that demonstrates its usage:

const provider = new ethers.JsonRpcProvider(
    "https://eth.llamarpc.com"
);

const currentBlockNumber: number = 18315860;
console.log(`Current Block Number: ${currentBlockNumber}`);

const contract: ethers.Contract = new ethers.Contract(
    "0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f",
    abi,
    provider
);

let filter = (contract.filters as any).PairCreated();

let logs = await contract.queryFilter(
    filter,
    currentBlockNumber - 50,
    currentBlockNumber - 1,
);

console.log(`Logs related to PairCreated (${logs.length}): ${JSON.stringify(logs)}`);

The queryFilter() method essentially wraps around the getLogs() method. It does the necessary work to structure the filter correctly, ensuring that logs specific to the contract and event in question are fetched. You can find the underlying implementation of queryFilter() in ethers v6 here: https://github.com/ethers-io/ethers.js/blob/main/src.ts/contract/contract.ts#L933

Best Answer

Related Solutions

[Ethereum] watching all the events of a contract (geth): ‘cannot find event for log undefined: undefined’

Update Responding To Comments Below

Etherscan – Querying Events Using Ethers.js Returns Logs with Unrelated Contract Addresses

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