Encode a solidity struct in using etherjs

encode_struct_in_js

// consider our struct to be:
/** 
struct TaskReward {
        uint256 igoId;
        Tier tier;
        address rewardee;
        uint256 taskId;
}
*/

const ethers = require('ethers');

async function sign(
    igoId = 1,
    tier = 0,
    addr = '0x295e26495cef6f69dfa69911d9d8e4f3bbadb89b',
    taskId = 23512345
) {
    const coder = ethers.utils.defaultAbiCoder;

    const coded = coder.encode(
        ['tuple(uint256, uint8, address, uint256)'], // an enum is always a uint8
        [[igoId, tier, addr, taskId]]
    );
    
    // you can then hash the encoded struct in `coded`
    // but you can't use `ethers.utils.solidityKeccak256` to 
    // encode & hash a struct in one call

    process.stdout.write(coded);
}

sign()
    .then(() => process.exit(0))
    .catch((error) => {
        console.error(error);
        process.exit(1);
    });