What is input in web3.eth.abi.decodeLog(inputs, hexString, topics);

Question

web3.eth.abi.decodeLog([{

type: 'string',
name: 'myString'

} , {

type: 'uint256',
name: 'myNumber',
indexed: true

},{

type: 'uint8',
name: 'mySmallNumber',
indexed: true

}], '0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000748656c6c6f252100000000000000000000000000000000000000000000000000', ['0x000000000000000000000000000000000000000000000000000000000000f310', '0x0000000000000000000000000000000000000000000000000000000000000010']);

Result { '0': 'Hello%!', '1': '62224', '2': '16', myString: 'Hello%!', myNumber: '62224', mySmallNumber: '16' }

this is decodelog example in "https://web3js.readthedocs.io/en/v1.2.0/web3-eth-abi.html#decodelog" but i don't know how to find "inputs" parameters.

Thanks for reading

Answer 1

inputs parameter is json object of your event parameters from the smart contract. For example Chainlink contract transfer event is event Transfer(address indexed from, address indexed to, uint256 value);. Now if we want to decode this event the input parameter will look like this:

[{
    type: 'address',
    name: 'from',
    indexed: true
},{
    type: 'address',
    name: 'to',
    indexed: true
},{
    type: 'uint256',
    name: 'value'
}]

Now in order to fully decode the event log we need the rest two parameters which are hexString and topics. Let's take for example this random transaction and use it event log data. Example:

web3.eth.abi.decodeLog([{
    type: 'address',
    name: 'from',
    indexed: true
},{
    type: 'address',
    name: 'to',
    indexed: true
},{
    type: 'uint256',
    name: 'value'
}],
'0000000000000000000000000000000000000000000000041b9ece2305db9c00',
['0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef', '0x00000000000000000000000059a5208b32e627891c389ebafc644145224006e8', '0x0000000000000000000000004e2e464420f1392ba08282644feba1bf650e1cc6']);

When you execute this code you will see what values have been passed and saved for this event log.