bot.js

// Intianiate Web3 connection
const Web3 = require('web3')
const web3 = new Web3('ws://127.0.0.1:7545') // Replace this with a websocket connection to your alchemy node to monitor mainnet

const IUniswapV2Factory = require("@uniswap/v2-core/build/IUniswapV2Factory.json")
const IUniswapV2Router02 = require('@uniswap/v2-periphery/build/IUniswapV2Router02.json')
const IUniswapV2Pair = require('@uniswap/v2-core/build/IUniswapV2Pair.json')
const IERC20 = require('@openzeppelin/contracts/build/contracts/ERC20.json')

const uFactoryAddress = '0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f'
const uRouterAddress = '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D'

const uFactory = new web3.eth.Contract(IUniswapV2Factory.abi, uFactoryAddress)
const uRouter = new web3.eth.Contract(IUniswapV2Router02.abi, uRouterAddress)
const WETH = new web3.eth.Contract(IERC20.abi, '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2')

const AMOUNT = '0.25' // How much WETH are you willing to spend on new tokens?
const SLIPPAGE = 0.05 // 5% Slippage

const main = async () => {

    const [deployer, sniper] = await web3.eth.getAccounts()

    // Create event listener to listen to PairCreated
    uFactory.events.PairCreated({}, async (error, event) => {
        console.log(`New pair detected...\n`)

        const { token0, token1, pair } = event.returnValues
        console.log(`Token0: ${token0}`)
        console.log(`Token1: ${token1}`)
        console.log(`Pair Address: ${pair}\n`)

        // Since we are buying this new token with WETH, we want to verify token0 & token1 address, and fetch the address of the new token?
        let path = []

        if (token0 === WETH._address) {
            path = [token0, token1]
        }

        if (token1 === WETH._address) {
            path = [token1, token0]
        }

        if (path.length === 0) {
            console.log(`Pair wasn\'t created with WETH...\n`)
            return
        }

        const uPair = new web3.eth.Contract(IUniswapV2Pair.abi, pair)
        const token = new web3.eth.Contract(IERC20.abi, path[1]) // Path[1] will always be the token we are buying.

        console.log(`Checking liquidity...\n`)

        // Ideally you'll probably want to take a closer look at reserves, and price from the pair address
        // to determine if you want to snipe this particular token...
        const reserves = await uPair.methods.getReserves().call()

        if (reserves[0] == 0 && reserves[1] == 0) {
            console.log(`Token has no liquidity...`)
            return
        }

        console.log(`Swapping WETH...\n`)

        try {
            const amountIn = new web3.utils.BN(web3.utils.toWei(AMOUNT, 'ether'))
            const amounts = await uRouter.methods.getAmountsOut(amountIn, path).call()
            const amountOut = String(amounts[1] - (amounts[1] * SLIPPAGE))
            const deadline = Date.now() + 1000 * 60 * 10

            await WETH.methods.approve(uRouter._address, amountIn).send({ from: sniper })

            const gas = await uRouter.methods.swapExactTokensForTokens(amountIn, amountOut, path, sniper, deadline).estimateGas({ from: sniper })
            await uRouter.methods.swapExactTokensForTokens(amountIn, amountOut, path, sniper, deadline).send({ from: sniper, gas: gas })

            console.log(`Swap Successful\n`)

            // Check user balance of token:
            const symbol = await token.methods.symbol().call()
            const tokenBalance = await token.methods.balanceOf(sniper).call()

            console.log(`Successfully swapped ${AMOUNT} WETH for ${web3.utils.fromWei(tokenBalance.toString(), 'ether')} ${symbol}\n`)
        } catch (error) {
            console.log(`Error Occured while swapping...`)
            console.log(`You may need to adjust slippage, or amountIn.\n`)
            console.log(error)
        }

        console.log(`Listening for new pairs...\n`)

    })

    console.log(`Listening for new pairs...\n`)
}

main()