Create your own Etherscan with React in 5 minutes

In this tutorial, we'll create a simple single-page etherscan in reactjs. For the clean UI, we are going to use the amazing  

 which is the official react integration for 

I am assuming that you have a basic understanding of reactjs and components.

// this command will install create-react-app
npx create-react-app etherscan-react

 is the name of the project. You can name it anything you like.

Once it is installed, open the terminal in the project and run 

Following packages are required in this project.

We are going to use Etherscan API to get the ethereum blockchain data like the latest block details, transaction detail, ether price etc. 

 to register for an Etherscan account. Sign in if you already registered.

Go to the API-Keys section on the left side.

 as the app name. You can give it any name.

You can check the latest version of semantic-ui from this 

Open the project in your favourite code editor. I am using VS Code. 

- src
	- components
		- Eth-Overview
		- Header
		- Latest-Blocks
		- Latest-Txs 

Header
	- Header.jsx
	- header.css
	- index.js

import React from "react";
// import Header component from the semantic-ui-react
import { Header } from "semantic-ui-react";
import "./header.css";

function AppDashboard() {
  return (
    <div>
      <Header as="h2" block>
        Ethereum
      </Header>
    </div>
  );
}

export default AppDashboard;

Here we are creating a function component by name 

 and then we are exporting it at line 16. 

.ui.block.header {
  text-align: left;
  background: white;
  color: #1d6fa5;
  box-shadow: 1px 1px #1d6fa5;
  margin: 10px;
}

import AppHeader from "./Header.jsx";

export default AppHeader;

import React from "react";
// import the Header component
import Header from "./components/Header/index";

function App() {
  return (
    <div>
      <Header></Header>
    </div>
  );
}

export default App;

Open the terminal in the project's root directory and run 

Eth-Overview
	- Eth-Overview.jsx
	- eth-overview.css
	- index.js

import React, { Component } from "react";
import axios from "axios";
import "./eth-overview.css";
import { Card, Grid, Icon } from "semantic-ui-react";
import LatestBlocks from "../Latest-Blocks/index";
import LatestTxs from "../Latest-Txs/index";

// import api key from the env variable
const apiKey = process.env.REACT_APP_ETHERSCAN_API_KEY;

const endpoint = `https://api.etherscan.io/api`;

class EthOverview extends Component {
  constructor() {
    super();
    this.state = {
      ethUSD: "",
      ethBTC: "",
      blockNo: "",
      latestBlock: 0,
      difficulty: "",
      marketCap: 0
    };
  }

  async componentDidMount() {
    // get the ethereum price
    axios
      .get(endpoint + `?module=stats&action=ethprice&apikey=${apiKey}`)
      .then(res => {
        const { result } = res.data;
        this.setState(
          {
            ethUSD: result.ethusd,
            ethBTC: result.ethbtc
          },
          () => {
            // get the market cap of ether in USD
            axios
              .get(endpoint + `?module=stats&action=ethsupply&apikey=${apiKey}`)
              .then(res => {
                const { result } = res.data;
                // in wei
                const priceWei = result.toString();

                // in ether
                const priceEth = priceWei.slice(0, priceWei.length - 18);
                console.log(result, priceWei, priceEth);
                // convert eth in USD
                this.setState({
                  marketCap: parseInt(priceEth) * this.state.ethUSD
                });
              });
          }
        );
      });

    // get the latest block number
    axios
      .get(endpoint + `?module=proxy&action=eth_blockNumber&apikey=${apiKey}`)
      .then(res => {
        this.setState({
          latestBlock: parseInt(res.data.result),
          blockNo: res.data.result // save block no in hex
        });

        // get the block difficulty
        axios
          .get(
            endpoint +
              `?module=proxy&action=eth_getBlockByNumber&tag=${res.data.result}&boolean=true&apikey=${apiKey}`
          )
          .then(blockDetail => {
            const { result } = blockDetail.data;

            const difficulty = parseInt(result.difficulty).toString();

            // convert difficulty in Terra Hash
            // instead of dividing it with 10^12 we'll slice it
            const difficultyTH = `${difficulty.slice(0, 4)}.${difficulty.slice(
              4,
              6
            )} TH`;

            this.setState({
              difficulty: difficultyTH
            });
          });
      });
  }

  getLatestBlocks = () => {
    if (this.state.latestBlock) {
      return <LatestBlocks latestBlock={this.state.latestBlock}></LatestBlocks>;
    }
  };

  getLatestTxs = () => {
    if (this.state.blockNo) {
      return <LatestTxs blockNo={this.state.blockNo}></LatestTxs>;
    }
  };

  render() {
    const { ethUSD, ethBTC, latestBlock, difficulty, marketCap } = this.state;
    return (
      <div>
        <Grid>
          <Grid.Row>
            <Grid.Column width={4}>
              <Card>
                <Card.Content>
                  <Card.Header style={{ color: "#1d6fa5" }}>
                    <Icon name="ethereum"></Icon> ETHER PRICE
                  </Card.Header>
                  <Card.Description textAlign="left">
                    <Icon name="usd"></Icon>
                    {ethUSD} <Icon name="at"></Icon> {ethBTC}{" "}
                    <Icon name="bitcoin"></Icon>
                  </Card.Description>
                </Card.Content>
              </Card>
            </Grid.Column>
            <Grid.Column width={4}>
              <Card>
                <Card.Content>
                  <Card.Header style={{ color: "#1d6fa5" }}>
                    <Icon name="list alternate outline"></Icon> LATEST BLOCK
                  </Card.Header>
                  <Card.Description textAlign="left">
                    <Icon name="square"></Icon> {latestBlock}
                  </Card.Description>
                </Card.Content>
              </Card>
            </Grid.Column>
            <Grid.Column width={4}>
              <Card>
                <Card.Content>
                  <Card.Header style={{ color: "#1d6fa5" }}>
                    <Icon name="setting"></Icon> DIFFICULTY
                  </Card.Header>
                  <Card.Description textAlign="left">
                    {difficulty}
                  </Card.Description>
                </Card.Content>
              </Card>
            </Grid.Column>
            <Grid.Column width={4}>
              <Card>
                <Card.Content>
                  <Card.Header style={{ color: "#1d6fa5" }}>
                    <Icon name="world"></Icon> MARKET CAP
                  </Card.Header>
                  <Card.Description textAlign="left">
                    <Icon name="usd"></Icon> {marketCap}
                  </Card.Description>
                </Card.Content>
              </Card>
            </Grid.Column>
          </Grid.Row>
        </Grid>

        <Grid divided="vertically">
          <Grid.Row columns={2}>
            <Grid.Column>{this.getLatestBlocks()}</Grid.Column>
            <Grid.Column>{this.getLatestTxs()}</Grid.Column>
          </Grid.Row>
        </Grid>
      </div>
    );
  }
}

export default EthOverview;

Don't panic, let me breakdown the code for you so that you can understand.

Latest-Blocks
	- Latest-Blocks.jsx
	- index.js

in the code editor and paste the below code.

import React, { Component } from "react";
import {
  Table,
  Label
} from "semantic-ui-react";

import axios from "axios";

const apiKey = process.env.REACT_APP_ETHERSCAN_API_KEY;
const endpoint = `https://api.etherscan.io/api`;

class LatestBlocks extends Component {
  constructor(props) {
    super(props);
    this.state = {
      blocks: []
    };
  }

  componentDidMount = () => {
    this.getBlocks();
  };

  getBlocks = async () => {
    const { latestBlock } = this.props;

    let blocks = [];

    for (let i = 0; i < 5; i = i + 1) {
      // get the block transaction
      const blockDetail = await axios.get(
        endpoint +
          `?module=proxy&action=eth_getBlockByNumber&tag=${(
            latestBlock - i
          ).toString(16)}&boolean=true&apikey=${apiKey}`
      );

      const { result } = blockDetail.data;
      blocks.push(
        <Table.Row key={i}>
          <Table.Cell>
            <Label color="blue">Bk</Label> {latestBlock - i}
          </Table.Cell>
          <Table.Cell>
            Miner {result.miner} <br></br>
            Txs {result.transactions.length}
          </Table.Cell>
          <Table.Cell>
            <Label color="blue">Size </Label> {parseInt(result.size)} bytes
          </Table.Cell>
        </Table.Row>
      );

      this.setState({
        blocks: blocks
      });
    }
  };

  render() {
    return (
      <Table fixed>
        <Table.Header>
          <Table.Row>
            <Table.Cell style={{ color: "#1d6fa5" }}>
              <h4>Latest Blocks</h4>
            </Table.Cell>
          </Table.Row>
        </Table.Header>

        <Table.Body>{this.state.blocks}</Table.Body>
      </Table>
    );
  }
}

export default LatestBlocks;

This component will fetch the latest 5 blocks from the etherscan and returns the table. You can increase the no. of blocks to fetch inline 29. 

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Amelia Wattenberger

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