Encode an integer to a uint256 to call a function

Question

I have the following task. I have a contract, which I don't have the source code for, so what I have is the contract's function selector: 0xddc24be3. The function accepts a uint256 as an argument. When I make the call to the function through web3 lib, I need to encode the given integer and append it in the data field along with the function selector. Question is how do I encode it correctly, using JS/ts-node?

Answer 1

const Web3 = require("web3");
const web3 = new Web3(); // You can also pass a provider URL here

// Your uint256 value
const uintValue = "10";

// Encode the uint256 value
const encodedValue = web3.eth.abi.encodeParameter("uint256", uintValue);

console.log("Encoded Value:", encodedValue);
const prex = "0xddc24be3";

const postx = prex + encodedValue.substring(2);

console.log("Postx:", postx);

Encoded Value: 0x000000000000000000000000000000000000000000000000000000000000000a

Postx: 0xddc24be3000000000000000000000000000000000000000000000000000000000000000a