eosjs ecc sha256 produce different hash than the EOS cpp sha256

Question

I should compare two hashes and the scenario is the following:

I create a new record in the contract as I pass eosjs-ecc sha256 generated hash as string. Let name it hashA. When I want to update the record, I should pass the plain data to the contract and the contract should hash it. Let name the resulted hash - hashB.
Unfortunately when I am comparing the hashA to hashB, they are always different

The code example is here:

1) eosjs-ecc hashing ->

let a = eosECC.sha256(JSON.stringify("Hello)); eosECC.sha256(Buffer.from(a, 'hex'))

2) Contract hashing ->

ACTION mycontract::update(name account, const string data)
{
   require_auth(account);

    auto iteratorDataRecord = recordTable.find(0);

    checksum256 sum = sha256(const_cast<char *>(data.c_str()), data.size());

    print("EOS cpp hash", sum);

    // iteratorDataRecord->hashed_data is string
    print("eosjs-ecc hash", iteratorDataRecord->hashed_data);
}

I am calling the contract action in this way :

cleos push action mycontract update '{"account": "myself", "data":"Hello"}' -p myself@active

Do I have to convert from checksum to hex and if so how to do that ?

Answer 1

Check the output of JSON.stringify, I think you'll be surprised to see that it adds quotation marks around the string. "Hello" is not the same as JSON.stringify("Hello")

JSON.stringify("Hello")=="\"Hello\""