Building a Web3 App - Crypto Gas Tracker

What is this post about ?

Hello fellow humanoids. Blockchain has made it way one way or another in your life, if you have already dug deep in rabbit hole then you might know how expensive transaction fees can become on certain chains E.g: Ethereum.
Check out the app here : Crypto gas tracker

Content

Setup NextJS
Get address from metamask
Fetch transaction details
Calculate Gas Fee

Lets go deep dive into each one and explore how it was implemented.

Setup NextJS

Next JS is a framework (built on-top of React JS) that allows us to create pre-rendered React websites. Follow this link to get yourself started on the setup

Get address from metamask

For this case we would be using metamask as our wallet. You can choose any as per your preference. Using Web3 apis we can connect to metamask and fetch the current network address of the user.

	const getBlockchainInformation = async () => {
	if (window.ethereum) {
	console.log("Metamask");
	window.web3 = new Web3(window.ethereum);
	await window.ethereum.enable();
	const ethereum = window.ethereum;
	const walletAddress = ethereum.selectedAddress;
	console.log("Wallet address", walletAddress);
	} else if (window.web3) {
	console.log("Update metamask");
	alert("Update metamask");
	} else {
	console.log("Install metamask");
	alert("Install metamask");
	}
	};

view raw getBlockchainInfo.js hosted with ❤ by GitHub

Fetch transaction details

For fetching transactions we would be using Etherscan API to fetch the transaction details for the given address

	//Client Side Code
	const getTransactions = async (address) => {
	const url = `/api/etherscan?address=${address}`;
	const response = await fetch(url).then((resp) => resp.json());
	return response?.result ?? [];
	};

	//Api route code
	export default async function handler(req, res) {
	// Run cors
	await cors(req, res);
	const query = req.query;
	const etherscanApiKey= process.env.ETHERSCAN_API_KEY;
	const url = `https://api.etherscan.io/api?module=account&action=txlist&address=${query?.address}&startblock=0&endblock=99999999&sort=asc&apikey=${etherscanApiKey}`;
	const response = await fetch(url).then(resp => resp.json());
	res.json(response);
	}

view raw getTransactionDetails.js hosted with ❤ by GitHub

Calculate Gas Fee

As per the API response the fields gasUsed and gasPrice are used to get the total eth spent.

gasFee = gasUsed * gasPrice

Since ETHUSD pair price is very volatile, we would fetch the ETHUSD on the date of the transaction using Coingecko api

	// Client side
	useEffect(() => {
	const fn = async () => {
	const transactions =
	trnxs?.map(async (trnx) => {
	const trnxDate = new Date(trnx.timeStamp * 1000);
	let formatted_date =
	trnxDate.getDate() +
	"-" +
	(trnxDate.getMonth() + 1) +
	"-" +
	trnxDate.getFullYear();
	const ethPriceHistoryUrl = `/api/coingecko-history?date=${formatted_date}`;
	const historyData = await fetch(ethPriceHistoryUrl).then((resp) =>
	resp.json()
	);
	const ethUSD = historyData?.market_data?.current_price?.usd;
	return {
	...trnx,
	gasFee: (trnx.gasPrice * trnx.gasUsed * ethUSD) / 1e18,
	gasFeeEth: (trnx.gasPrice * trnx.gasUsed) / 1e18,
	ethUSD: ethUSD,
	};
	}) ?? [];
	const values = await Promise.all(transactions);
	setUpdatedTrnxs(values);
	};
	fn();
	}, [trnxs]);

	// Api route
	export default async function handler(req, res) {
	// Run cors
	await cors(req, res);
	const query = req.query;
	const url = `https://api.coingecko.com/api/v3/coins/ethereum/history?date=${query?.date}`;
	const response = await fetch(url).then(resp => resp.json());
	res.json(response);
	}

view raw fetchETHUSD.js hosted with ❤ by GitHub

Conclusion

This app was made as part of learning Web3 apps. There might be bugs and enhancements on the way. Please feel free to provide feedback.
Stay safe and lend a hand to another :)