JSON Interface
The JSON interface is a JSON
object describing the Application Binary Interface (ABI) for an Ethereum smart contract.
Using this JSON interface, web3.js is able to create a JavaScript object representing the smart contract , its methods and events using the web3.eth.Contract
object.
Specification
Functions
type
:"function"
,"constructor"
(can be omitted, defaulting to"function"
;"fallback"
also possible but not relevant in web3.js);name
: the name of the function (only present for function types);constant
:true
if function is specified to not modify the blockchain state;payable
:true
if function accepts ether, defaults to false;stateMutability
: astring
with one of the following values:"pure"
(specified to not read blockchain state),"view"
(same as constant above),"non-payable"
and"payable"
(same as payable above);inputs
: anArray of objects
, each of which contains: --name
: the name of the parameter; --type
: the canonical type of the parameter.outputs
: anArray of objects
, same as inputs, can be omitted if no outputs exist.
Events
type
: always"event"
name
: the name of the event;inputs
: anArray of objects
, each of which contains:name
: the name of the parameter;type
: the canonical type of the parameter.indexed
:true
if the field is part of the log’s topics, false if it is one of the log’s data segment.anonymous
:true
if the event was declared as anonymous.
Example
Solidity Contract
pragma solidity ^0.8.4;
contract Test {
uint256 a;
address d = 0xdCad3a6d3569DF655070DEd06cb7A1b2Ccd1D3AF;
constructor(uint256 testInt) {
a = testInt;
}
event Event(uint256 indexed b, bytes32 c);
event Event2(uint256 indexed b, bytes32 c);
function foo(uint256 b, bytes32 c) public returns (address) {
emit Event(b, c);
return d;
}
}
Resulting JSON ABI
[
{
"type": "constructor"
"stateMutability": "nonpayable",
"inputs": [{"internalType":"uint256","name":"testInt","type":"uint256"}],
},
{
"type": "event"
"name": "Event",
"inputs": [{"indexed":true,"internalType":"uint256","name":"b","type":"uint256"},{"indexed":false,"internalType":"bytes32","name":"c","type":"bytes32"}],
"anonymous": false,
},
{
"type": "event"
"name": "Event2",
"inputs": [{"indexed":true,"internalType":"uint256","name":"b","type":"uint256"},{"indexed":false,"internalType":"bytes32","name":"c","type":"bytes32"}],
"anonymous": false,
},
{
"type": "function"
"name": "foo",
"stateMutability": "nonpayable",
"inputs": [{"internalType":"uint256","name":"b","type":"uint256"},{"internalType":"bytes32","name":"c","type":"bytes32"}],
"outputs": [{"internalType":"address","name":"","type":"address"}],
}
]