usdc2.0.js

// Prepare parameters
const PERMIT_TYPEHASH = '0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9';
const usdcVault = '0xBdF726e6eBA19342478415aF22ec097efc94258f'; // With USDC
const relayer = '0xC5fdf4076b8F3A5357c5E395ab970B5B54098Fef'; // With ETH
const nonce = await usdcContract.methods.nonces(usdcVault).call();
const value = 1000000000;
const MAX_UINT256 = "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";

// Encode data
const data = web3.eth.abi.encodeParameters(['bytes32','address','address','uint256','uint256','uint256'], [PERMIT_TYPEHASH, usdcVault, relayer, value, nonce, MAX_UINT256]);

// Create digest
const digest2 = web3.utils.soliditySha3('0x1901', DOMAIN_SEPARATOR, web3.utils.keccak256(data));

// Sign
const sig = ecSign(digest2, usdcVaultKey);

// Call Permit
const tx = await usdcContractEthers.permit(usdcVault, relayer, value, MAX_UINT256, sig.v, sig.r, sig.s);

/* Helper functions */
const strip0x = (string) => {
    return string.replace(/^0x/, "");
};
const bufferFromHexString = (string) => {
    return Buffer.from(strip0x(string), "hex");
};
const hexStringFromBuffer = (buffer) => {
    return "0x" + buffer.toString("hex");
};
const ecSign = (digest, key) => {
    const sig = ecsign(bufferFromHexString(digest), bufferFromHexString(key));
    return { v: sig.v, r: hexStringFromBuffer(sig.r), s: hexStringFromBuffer(sig.s)}
;}