OpenZeppelin Multicall

MakerDAOMulticall.sol

// SPDX-License-Identifier: MIT


pragma solidity >=0.5.0;
pragma experimental ABIEncoderV2;

/// @title Multicall - Aggregate results from multiple read-only function calls
/// @author Michael Elliot <mike@makerdao.com>
/// @author Joshua Levine <joshua@makerdao.com>
/// @author Nick Johnson <arachnid@notdot.net>

contract Multicall {
    struct Call {
        address target;
        bytes callData;
    }
    function aggregate(Call[] memory calls) public returns (uint256 blockNumber, bytes[] memory returnData) {
        blockNumber = block.number;
        returnData = new bytes[](calls.length);
        for(uint256 i = 0; i < calls.length; i++) {
            (bool success, bytes memory ret) = calls[i].target.call(calls[i].callData);
            require(success);
            returnData[i] = ret;
        }
    }
    // Helper functions
    function getEthBalance(address addr) public view returns (uint256 balance) {
        balance = addr.balance;
    }
    function getBlockHash(uint256 blockNumber) public view returns (bytes32 blockHash) {
        blockHash = blockhash(blockNumber);
    }
    function getLastBlockHash() public view returns (bytes32 blockHash) {
        blockHash = blockhash(block.number - 1);
    }
    function getCurrentBlockTimestamp() public view returns (uint256 timestamp) {
        timestamp = block.timestamp;
    }
    function getCurrentBlockDifficulty() public view returns (uint256 difficulty) {
        difficulty = block.difficulty;
    }
    function getCurrentBlockGasLimit() public view returns (uint256 gaslimit) {
        gaslimit = block.gaslimit;
    }
    function getCurrentBlockCoinbase() public view returns (address coinbase) {
        coinbase = block.coinbase;
    }
}

OpenZeppelinMulticall.sol

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Multicall.sol)

pragma solidity ^0.8.0;

import "./Address.sol";

/**
 * @dev Provides a function to batch together multiple calls in a single external call.
 *
 * _Available since v4.1._
 */
abstract contract Multicall {
    /**
     * @dev Receives and executes a batch of function calls on this contract.
     */
    function multicall(bytes[] calldata data) external virtual returns (bytes[] memory results) {
        results = new bytes[](data.length);
        for (uint256 i = 0; i < data.length; i++) {
            results[i] = Address.functionDelegateCall(address(this), data[i]);
        }
        return results;
    }
}

OpenZeppelinMulticallCaller.js

// An example using hardhat to create a contract and multicall the increment function n-times in a single transaction.
import { artifacts, ethers } from "hardhat";

async function main() {
    const Clicker = await ethers.getContractFactory("CookieClicker");

    const clicker = await Clicker.deploy()

    await clicker.deployed()
  
    const amt = 10 // times to multicall the same smart contract function
    
    // get the abi of the function you wish to call
    const inc = await getIncAbi()

    // call the multicall function
    var tx = await clicker.multicall(
        Array(amt).fill(inc) // makes an array with n-times the same element
    )
}

async function getIncAbi() {
    const artifact = await ethers.getContractFactory("CookieClicker");

    var functions = Object.keys(artifact.interface.functions)
    functions.forEach(function (part, index) {
        this[index] = "function " + part;
    }, functions);

    let iface = new ethers.utils.Interface(functions);

    return iface.encodeFunctionData("inc")
}

main()

OpenZeppelinMulticallCookieClicker.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/Multicall.sol";

contract CookieClicker is Multicall {
    int public cookies = 0;

    function inc() public {
        cookies++;
    }
}

OpenZeppelinMulticallERC20Token.sol

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/utils/Multicall.sol";

contract Token is ERC20, Multicall {
    constructor(uint256 initialSupply) ERC20("Gold", "GLD") {
        _mint(msg.sender, initialSupply);
    }
}