Params - a string array containing (required):
DATA(hex string, required)- the data in hex form to convert into a SHA3 hash.
web3_sha3takes in a hexadecimal number, not a direct string. So, if you wanted to convert "hello world" to it's Keccak-256 hash you would need to input the hex number for "hello world", which is "68656c6c6f20776f726c64".
DATA(hex string) - the Keccak-256 hash of the given string.