How to decode input data in ethersjs

Question

I am using ethersjs.

I use the following code to get data of transaction

var init = function () {
  var wss = new ethers.providers.WebSocketProvider(url);
      wss.getTransaction(tx).then(function (transaction) {
         wss.on("pending", (tx) => {
           console.log(transaction.data);
           }
      });
  });

Which will log something similar to

0x7ff36ab50000000000000000000000000000000000000000000000bc18ba4144048bbab00000000000000000000000000000000000000000000000000000000000000080000000000000000000000000c0c5eb43e2df059e3be6e4fb0284c283caa5991900000000000000000000000000000000000000000000000000000000614d87a80000000000000000000000000000000000000000000000000000000000000002000000000000000000000000bb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c00000000000000000000000008ba0619b1e7a582e0bce5bbe9843322c954c340

Which when decoded should be like below

0   amountOutMin    uint256 3469769694220364004016
1   path    address[]   bb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c
                        08ba0619b1e7a582e0bce5bbe9843322c954c340
2   to  address c0c5eb43e2df059e3be6e4fb0284c283caa59919
3   deadline    uint256 1632470952

I tried using parseTransaction as shown here but get function not defined. And also tried with decodeFunctionData but got same result that decodeFunctionData is not defined.

How can I get the information from the transaction data using ethers.js?

Thanks

Answer 1

You need the input types as well to be able to decode it.

const data = '0x7ff36ab50000000000000000000000000000000000000000000000bc18ba4144048bbab00000000000000000000000000000000000000000000000000000000000000080000000000000000000000000c0c5eb43e2df059e3be6e4fb0284c283caa5991900000000000000000000000000000000000000000000000000000000614d87a80000000000000000000000000000000000000000000000000000000000000002000000000000000000000000bb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c00000000000000000000000008ba0619b1e7a582e0bce5bbe9843322c954c340';

ethers.utils.defaultAbiCoder.decode(
  ['uint256', 'address[]', 'address', 'uint256'],
  ethers.utils.hexDataSlice(data, 4)
)
// gives: [e, ["0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c", "0x08ba0619b1e7A582E0BCe5BBE9843322C954C340"], "0xC0C5eb43E2dF059e3Be6E4fb0284C283CAa59919", e] (4)

If plugging in the ABI is more convenient for you then you can use interface:

const iface = new ethers.utils.Interface(['function swapExactETHForTokens(uint256 amountOutMin, address[] path, address to, uint256 deadline)'])

iface.decodeFunctionData('swapExactETHForTokens', '0x7ff36ab50000000000000000000000000000000000000000000000bc18ba4144048bbab00000000000000000000000000000000000000000000000000000000000000080000000000000000000000000c0c5eb43e2df059e3be6e4fb0284c283caa5991900000000000000000000000000000000000000000000000000000000614d87a80000000000000000000000000000000000000000000000000000000000000002000000000000000000000000bb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c00000000000000000000000008ba0619b1e7a582e0bce5bbe9843322c954c340')
// gives: [e, ["0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c", "0x08ba0619b1e7A582E0BCe5BBE9843322C954C340"], "0xC0C5eb43E2dF059e3Be6E4fb0284C283CAa59919", e] (4)

---

For Ethers v6 you only need to remove the utils for instance:

ethers.defaultAbiCoder.decode(
  ['uint256', 'address[]', 'address', 'uint256'],
  ethers.dataSlice(data, 4)
)