Javascript

原生JS Web3Modal Demo (笔记)

本文主要是介绍原生JS Web3Modal Demo (笔记)，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！ 
<html>
  <head>
    <title>Simple vanilla JS example of Web3modal usage</title>

    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <!-- Get some bootstrap default styles -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
  </head>
  <body>
    <!-- Construct a Bootstrap layout -->
    <div class="container">
      <div class="row">
        <div class="col-md-12">
          <h1>Web3modal vanilla JavaScript demo</h1>

          <p>No wallet connected. Connect wallet to show accounts and their ETH balances.</p>

          <div id="prepare">
            <button class="btn btn-primary" id="btn-connect">
              Connect wallet
            </button>
          </div>

          <div id="connected" style="display: none">

            <button class="btn btn-primary" id="btn-disconnect">
              Disconnect wallet
            </button>

            <hr>

            <div id="network">
              <p>
                <strong>Connected blockchain:</strong> <span id="network-name"></span>
              </p>

              <p>
                <strong>Selected account:</strong> <span id="selected-account"></span>
              </p>

            </div>

            <hr>

            <h3>All account balances</h3>

            <table class="table table-listing">
              <thead>
                <th>Address</th>
                <th>ETH balance</th>
              </thead>

              <tbody id="accounts">
              </tbody>
            </table>

            <p>Please try to switch between different accounts in your wallet if your wallet supports this functonality.</p>

          </div>

        </div>
      </div>
    </div>

    <!-- We use simple <template> templating for the example -->
    <div id="templates" style="display: none">
      <template id="template-balance">
        <tr>
          <th class="address"></th>
          <td class="balance"></td>
        </tr>
      </template>
    </div>

    <!--

      Use unpkg CDN to load all NPM packages to vanilla Javascript - read more at http://unpkg.com

      On your deployment, you properly either want to use a preprocessing tool like webpack
      to include these files, or extract NPM archives and manually host the files inside.

      TODO: Pin down all versions.

    -->

    <script src="https://unpkg.com/web3@latest/dist/web3.min.js"></script>
    <script type="text/javascript" src="https://unpkg.com/web3modal"></script>
    <script type="text/javascript" src="https://unpkg.com/evm-chains/lib/index.js"></script>
    <script type="text/javascript" src="https://unpkg.com/@walletconnect/web3-provider"></script>
    <script type="text/javascript" src="https://unpkg.com/fortmatic@2.0.6/dist/fortmatic.js"></script>

    <!-- This is our example code -->
    <script type="text/javascript" src="./example.js"></script>
  </body>
</html>

"use strict";

/**
 * Example JavaScript code that interacts with the page and Web3 wallets
 */

 // Unpkg imports
const Web3Modal = window.Web3Modal.default;
const WalletConnectProvider = window.WalletConnectProvider.default;
const EvmChains = window.EvmChains;
const Fortmatic = window.Fortmatic;

// Web3modal instance
let web3Modal

// Chosen wallet provider given by the dialog window
let provider;


// Address of the selected account
let selectedAccount;


/**
 * Setup the orchestra
 */
function init() {

  console.log("Initializing example");
  console.log("WalletConnectProvider is", WalletConnectProvider);
  console.log("Fortmatic is", Fortmatic);

  // Tell Web3modal what providers we have available.
  // Built-in web browser provider (only one can exist as a time)
  // like MetaMask, Brave or Opera is added automatically by Web3modal
  const providerOptions = {
    walletconnect: {
      package: WalletConnectProvider,
      options: {
        // Mikko's test key - don't copy as your mileage may vary
        infuraId: "8043bb2cf99347b1bfadfb233c5325c0",
      }
    },

    fortmatic: {
      package: Fortmatic,
      options: {
        // Mikko's TESTNET api key
        key: "pk_test_391E26A3B43A3350"
      }
    }
  };

  web3Modal = new Web3Modal({
    cacheProvider: false, // optional
    providerOptions, // required
  });

}


/**
 * Kick in the UI action after Web3modal dialog has chosen a provider
 */
async function fetchAccountData() {

  // Get a Web3 instance for the wallet
  const web3 = new Web3(provider);

  console.log("Web3 instance is", web3);

  // Get connected chain id from Ethereum node
  const chainId = await web3.eth.getChainId();
  // Load chain information over an HTTP API
  const chainData = await EvmChains.getChain(chainId);
  document.querySelector("#network-name").textContent = chainData.name;

  // Get list of accounts of the connected wallet
  const accounts = await web3.eth.getAccounts();

  // MetaMask does not give you all accounts, only the selected account
  console.log("Got accounts", accounts);
  selectedAccount = accounts[0];

  document.querySelector("#selected-account").textContent = selectedAccount;

  // Get a handl
  const template = document.querySelector("#template-balance");
  const accountContainer = document.querySelector("#accounts");

  // Purge UI elements any previously loaded accounts
  accountContainer.innerHTML = '';

  // Go through all accounts and get their ETH balance
  const rowResolvers = accounts.map(async (address) => {
    const balance = await web3.eth.getBalance(address);
    // ethBalance is a BigNumber instance
    // https://github.com/indutny/bn.js/
    const ethBalance = web3.utils.fromWei(balance, "ether");
    const humanFriendlyBalance = parseFloat(ethBalance).toFixed(4);
    // Fill in the templated row and put in the document
    const clone = template.content.cloneNode(true);
    clone.querySelector(".address").textContent = address;
    clone.querySelector(".balance").textContent = humanFriendlyBalance;
    accountContainer.appendChild(clone);
  });

  // Because rendering account does its own RPC commucation
  // with Ethereum node, we do not want to display any results
  // until data for all accounts is loaded
  await Promise.all(rowResolvers);

  // Display fully loaded UI for wallet data
  document.querySelector("#prepare").style.display = "none";
  document.querySelector("#connected").style.display = "block";
}



/**
 * Fetch account data for UI when
 * - User switches accounts in wallet
 * - User switches networks in wallet
 * - User connects wallet initially
 */
async function refreshAccountData() {

  // If any current data is displayed when
  // the user is switching acounts in the wallet
  // immediate hide this data
  document.querySelector("#connected").style.display = "none";
  document.querySelector("#prepare").style.display = "block";

  // Disable button while UI is loading.
  // fetchAccountData() will take a while as it communicates
  // with Ethereum node via JSON-RPC and loads chain data
  // over an API call.
  document.querySelector("#btn-connect").setAttribute("disabled", "disabled")
  await fetchAccountData(provider);
  document.querySelector("#btn-connect").removeAttribute("disabled")
}


/**
 * Connect wallet button pressed.
 */
async function onConnect() {

  console.log("Opening a dialog", web3Modal);
  try {
    provider = await web3Modal.connect();
  } catch(e) {
    console.log("Could not get a wallet connection", e);
    return;
  }

  // Subscribe to accounts change
  provider.on("accountsChanged", (accounts) => {
    fetchAccountData();
  });

  // Subscribe to chainId change
  provider.on("chainChanged", (chainId) => {
    fetchAccountData();
  });

  // Subscribe to networkId change
  provider.on("networkChanged", (networkId) => {
    fetchAccountData();
  });

  await refreshAccountData();
}

/**
 * Disconnect wallet button pressed.
 */
async function onDisconnect() {

  console.log("Killing the wallet connection", provider);

  // TODO: Which providers have close method?
  if(provider.close) {
    await provider.close();

    // If the cached provider is not cleared,
    // WalletConnect will default to the existing session
    // and does not allow to re-scan the QR code with a new wallet.
    // Depending on your use case you may want or want not his behavir.
    await web3Modal.clearCachedProvider();
    provider = null;
  }

  selectedAccount = null;

  // Set the UI back to the initial state
  document.querySelector("#prepare").style.display = "block";
  document.querySelector("#connected").style.display = "none";
}


/**
 * Main entry point.
 */
window.addEventListener('load', async () => {
  init();
  document.querySelector("#btn-connect").addEventListener("click", onConnect);
  document.querySelector("#btn-disconnect").addEventListener("click", onDisconnect);
});
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